{ "title": "Reaction atlas", "author": "J. Skowronski", "url": "https://jskowron.eu/atlas", "version": "2026-10-12", "licence": { "name": "CC BY 4.0", "url": "https://creativecommons.org/licenses/by/4.0/" }, "cite": "J. Skowronski, Reaction atlas, version 2026-10-12, https://jskowron.eu/atlas.", "generated": "2026-10-16T11:39:47.204Z", "conventions": { "energies": "keV, centre of mass, unless a field says otherwise; Q-values in MeV", "qValue": "Q = Σ Δ(initial) − Σ Δ(final) with AME2020 atomic mass excesses. Where a positron is emitted, Q includes the 2 mₑc² released when it annihilates (annihilation: true); kinetic = Q − 2 mₑc².", "gamow": "E0 = 0.1220 (Z1² Z2² μ T9²)^(1/3) MeV, width = 0.2368 (Z1² Z2² μ T9⁵)^(1/6) MeV, μ in u from AME2020; values in keV. For an endothermic reaction (Q < 0) whose window would reach below the threshold −Q, the window is threshold-limited (thresholdLimited: true): it runs from lo = max(threshold, lower 1/e point) to hi, the energy above the maximum at which exp(−E/kT − 2πη) has fallen by 1/e; E0 is then that maximum and width = hi − lo.", "halfLife": "NUBASE2020, seconds (null for stable nuclides)." }, "families": [ { "id": "pp", "name": "The proton–proton chains", "summary": "How the Sun shines. Four protons become one helium nucleus through a chain of reactions that starts with the slowest process in the Sun, the fusion of two protons.", "page": null, "onMap": true, "see": [], "networks": [ "pp1", "pp2", "pp3", "hep" ] }, { "id": "cno", "name": "The CNO cycles", "summary": "Carbon, nitrogen and oxygen act as catalysts that turn hydrogen into helium. In the Sun this gives about one per cent of the energy; in stars heavier than about 1.3 solar masses it is the main source.", "page": null, "onMap": true, "see": [], "networks": [ "cno1", "cno2", "cno3", "cno4" ] }, { "id": "nena", "name": "The NeNa cycle", "summary": "In red giants, AGB stars and novae, protons are captured on the neon isotopes and on sodium. The cycle sets the sodium abundance of stars, and the sodium–oxygen anticorrelation seen in globular clusters.", "page": null, "onMap": true, "see": [], "networks": [ "nena" ] }, { "id": "mgal", "name": "The MgAl cycle", "summary": "At still higher temperatures protons are captured on magnesium and aluminium. The cycle makes the radioactive ²⁶Al whose γ-ray line traces recent nucleosynthesis across the Galaxy.", "page": null, "onMap": true, "see": [], "networks": [ "mgal" ] }, { "id": "he", "name": "Helium burning", "summary": "Once the hydrogen is gone, the core contracts and heats until helium burns. Three helium nuclei make carbon, and carbon captures helium to make oxygen: the ratio of the two decides much of what follows.", "page": null, "onMap": true, "see": [], "networks": [ "he-burning" ] }, { "id": "carbon", "name": "Carbon burning", "summary": "After helium burning, the core of a star of more than about eight solar masses is made of carbon and oxygen. It contracts and heats until two carbon nuclei fuse, making neon, sodium and magnesium. The same fusion ignites type Ia supernovae and the X-ray superbursts of neutron stars.", "page": null, "onMap": true, "see": [], "networks": [ "carbon-burning" ] }, { "id": "neutrons", "name": "Neutron sources", "summary": "Elements heavier than iron are mostly built by neutron captures. In stars the neutrons come from two helium-induced reactions, on ¹³C and on ²²Ne.", "page": null, "onMap": true, "see": [ "s-process" ], "networks": [ "neutron-sources", "neutron-poisons" ] }, { "id": "s-process", "name": "The s-process", "summary": "Slow neutron captures build about half the nuclei between iron and bismuth. Each capture adds one neutron; an unstable nucleus usually decays before the next arrives, so the path climbs along the valley of stable nuclei up to lead and bismuth.", "page": "/atlas/s-process", "onMap": false, "see": [], "networks": [ "s-main", "s-weak" ] }, { "id": "bbn", "name": "Big Bang nucleosynthesis", "summary": "In the first minutes after the Big Bang the Universe made deuterium, helium and a little lithium. Comparing the predicted and observed amounts tests cosmology and particle physics.", "page": null, "onMap": true, "see": [], "networks": [ "bbn" ] } ], "networks": [ { "id": "pp1", "family": "pp", "name": "pp-I", "summary": "The main branch in the Sun: two protons make a deuteron, the deuteron captures a proton to make ³He, and two ³He nuclei fuse to ⁴He.", "temperatures": [ { "label": "centre of the Sun", "T9": 0.0157 } ], "reactions": [ "1H-pp-2H", "1H-pep-2H", "2H-pg-3He", "3He-3He2p-4He" ] }, { "id": "pp2", "family": "pp", "name": "pp-II", "summary": "³He captures a ⁴He nucleus to make ⁷Be, which captures an electron and becomes ⁷Li; ⁷Li and a proton give two ⁴He. Source of the ⁷Be solar neutrinos.", "temperatures": [ { "label": "centre of the Sun", "T9": 0.0157 } ], "reactions": [ "3He-ag-7Be", "7Be-ec-7Li", "7Li-pa-4He" ] }, { "id": "pp3", "family": "pp", "name": "pp-III", "summary": "A rare branch: ⁷Be captures a proton to make ⁸B, whose decay emits the high-energy solar neutrinos first detected in the Homestake mine.", "temperatures": [ { "label": "centre of the Sun", "T9": 0.0157 } ], "reactions": [ "3He-ag-7Be", "7Be-pg-8B", "8B-bp-8Be" ] }, { "id": "hep", "family": "pp", "name": "hep", "summary": "The rarest termination: a ³He nucleus captures a proton and becomes ⁴He directly, through the weak interaction. It adds almost nothing to the Sun's energy, but emits the most energetic solar neutrinos.", "temperatures": [ { "label": "centre of the Sun", "T9": 0.0157 } ], "reactions": [ "3He-hep-4He" ] }, { "id": "cno1", "family": "cno", "name": "CN cycle (CNO-I)", "summary": "Carbon captures a proton, decays, captures more protons and returns to carbon at the end, having turned four protons into one helium nucleus.", "temperatures": [ { "label": "centre of the Sun", "T9": 0.0157 }, { "label": "core of a 15 M☉ star", "T9": 0.035 } ], "reactions": [ "12C-pg-13N", "13N-bp-13C", "13C-pg-14N", "14N-pg-15O", "15O-bp-15N", "15N-pa-12C" ] }, { "id": "cno2", "family": "cno", "name": "CNO-II", "summary": "Rarely, ¹⁵N captures a proton and keeps it instead of emitting an alpha particle; the cycle then passes through oxygen and fluorine.", "temperatures": [ { "label": "core of a 15 M☉ star", "T9": 0.035 } ], "reactions": [ "15N-pg-16O", "16O-pg-17F", "17F-bp-17O", "17O-pa-14N" ] }, { "id": "cno3", "family": "cno", "name": "CNO-III", "summary": "A further branch through ¹⁸F and ¹⁸O, which matters in AGB stars and in nova explosions; the oxygen isotope ratios measured in presolar grains depend on it.", "temperatures": [ { "label": "AGB star", "T9": 0.05 }, { "label": "classical nova", "T9": 0.2 } ], "reactions": [ "17O-pg-18F", "18F-bp-18O", "18O-pa-15N" ] }, { "id": "cno4", "family": "cno", "name": "CNO-IV", "summary": "The last branch, through ¹⁹F. A proton capture on ¹⁹F that emits a γ-ray instead of an alpha particle leaks material out of the CNO cycles towards neon.", "temperatures": [ { "label": "AGB star", "T9": 0.05 }, { "label": "classical nova", "T9": 0.2 } ], "reactions": [ "18O-pg-19F", "19F-pa-16O", "19F-pg-20Ne" ] }, { "id": "nena", "family": "nena", "name": "NeNa cycle", "summary": "Proton captures on the neon isotopes and on ²³Na. They set the sodium abundance, and the sodium–oxygen anticorrelation seen in globular clusters.", "temperatures": [ { "label": "AGB hot-bottom burning", "T9": 0.08 }, { "label": "classical nova", "T9": 0.2 } ], "reactions": [ "20Ne-pg-21Na", "21Na-bp-21Ne", "21Ne-pg-22Na", "22Na-bp-22Ne", "22Ne-pg-23Na", "23Na-pa-20Ne", "23Na-pg-24Mg" ] }, { "id": "mgal", "family": "mgal", "name": "MgAl cycle", "summary": "Proton captures on the magnesium isotopes and on ²⁷Al. ²⁵Mg(p,γ)²⁶Al makes the radioactive ²⁶Al whose 1809 keV γ-ray line maps recent nucleosynthesis in the Galaxy.", "temperatures": [ { "label": "AGB hot-bottom burning", "T9": 0.08 }, { "label": "classical nova", "T9": 0.2 } ], "reactions": [ "24Mg-pg-25Al", "25Al-bp-25Mg", "25Mg-pg-26Al", "26Al-bp-26Mg", "26Mg-pg-27Al", "27Al-pa-24Mg", "27Al-pg-28Si" ] }, { "id": "he-burning", "family": "he", "name": "Helium burning", "summary": "The triple-alpha process makes ¹²C through the Hoyle state; alpha captures then make ¹⁶O and ²⁰Ne. ¹²C(α,γ)¹⁶O is often called the most important reaction in nuclear astrophysics.", "temperatures": [ { "label": "core helium burning", "T9": 0.2 } ], "reactions": [ "4He-aa-12C", "12C-ag-16O", "16O-ag-20Ne", "14N-ag-18F", "18F-bp-18O", "18O-ag-22Ne" ] }, { "id": "carbon-burning", "family": "carbon", "name": "Carbon burning", "summary": "Two ¹²C nuclei fuse into an excited ²⁴Mg, which breaks up into ²⁰Ne and an alpha particle or into ²³Na and a proton; rarely, above 2.6 MeV, into ²³Mg and a neutron. Protons captured on ²³Na give ²⁰Ne or ²⁴Mg.", "temperatures": [ { "label": "core carbon burning, 15 M☉ star", "T9": 0.83 }, { "label": "superburst ignition, accreting neutron star", "T9": 0.5 } ], "reactions": [ "12C-12Ca-20Ne", "12C-12Cp-23Na", "12C-12Cn-23Mg", "23Na-pa-20Ne", "23Na-pg-24Mg" ] }, { "id": "neutron-sources", "family": "neutrons", "name": "Neutron sources of the s-process", "summary": "¹³C(α,n)¹⁶O supplies the neutrons in low-mass AGB stars, ²²Ne(α,n)²⁵Mg in massive stars; ²²Ne(α,γ)²⁶Mg competes with the second.", "temperatures": [ { "label": "AGB ¹³C pocket", "T9": 0.09, "reactions": [ "13C-an-16O" ] }, { "label": "AGB thermal pulse", "T9": 0.27, "reactions": [ "22Ne-an-25Mg", "22Ne-ag-26Mg" ] }, { "label": "massive star, He core end", "T9": 0.3, "reactions": [ "22Ne-an-25Mg", "22Ne-ag-26Mg", "17O-an-20Ne" ] } ], "reactions": [ "13C-an-16O", "22Ne-an-25Mg", "22Ne-ag-26Mg", "17O-an-20Ne" ] }, { "id": "neutron-poisons", "family": "neutrons", "name": "Neutron poisons", "summary": "Light nuclei that are far more abundant than iron capture some of the neutrons before the heavy seeds can. ¹⁴N(n,p)¹⁴C competes in the ¹³C pocket of AGB stars; ²⁵Mg, made by the neutron source itself, ²²Ne and ¹⁶O capture neutrons in massive stars, and the ¹⁷O made from ¹⁶O can give its neutron back through ¹⁷O(α,n)²⁰Ne.", "temperatures": [ { "label": "AGB ¹³C pocket", "T9": 0.09, "reactions": [ "14N-np-14C" ] }, { "label": "massive star, core helium burning", "T9": 0.3, "reactions": [ "22Ne-ng-23Ne", "16O-ng-17O", "25Mg-ng-26Mg" ] } ], "reactions": [ "14N-np-14C", "22Ne-ng-23Ne", "16O-ng-17O", "25Mg-ng-26Mg" ] }, { "id": "s-main", "family": "s-process", "name": "Main component (AGB stars)", "summary": "In low-mass AGB stars, neutrons from the ¹³C pocket and, briefly, from ²²Ne in the thermal pulses carry iron seeds all the way to lead and bismuth. This component makes most of the s-process nuclei above mass 90.", "temperatures": [ { "label": "AGB ¹³C pocket", "T9": 0.09 }, { "label": "AGB thermal pulse", "T9": 0.27 } ], "reactions": [ "56Fe-ng-57Fe", "85Kr-ng-86Kr", "93Zr-ng-94Zr", "147Pm-ng-148Pm", "151Sm-ng-152Sm", "171Tm-ng-172Tm", "197Au-ng-198Au", "204Tl-ng-205Tl", "209Bi-ng-210Bi" ] }, { "id": "s-weak", "family": "s-process", "name": "Weak component (massive stars)", "summary": "In stars of more than about ten solar masses, ²²Ne(α,n)²⁵Mg releases neutrons at the end of core helium burning and again in carbon-burning shells. Too few neutrons per seed reach far: this component makes nuclei up to mass about 90, from copper to strontium.", "temperatures": [ { "label": "massive star, core helium burning", "T9": 0.3 }, { "label": "massive star, shell carbon burning", "T9": 1.04 } ], "reactions": [ "56Fe-ng-57Fe", "62Ni-ng-63Ni", "63Ni-ng-64Ni", "85Kr-ng-86Kr" ] }, { "id": "bbn", "family": "bbn", "name": "Big Bang nucleosynthesis", "summary": "A few minutes after the Big Bang, neutrons and protons combined into deuterium, ³He, ⁴He and ⁷Li. The predicted deuterium abundance depends on d(p,γ)³He, now measured at LUNA.", "temperatures": [ { "label": "deuterium bottleneck", "T9": 0.8 }, { "label": "end of BBN", "T9": 0.3 } ], "reactions": [ "1H-ng-2H", "2H-pg-3He", "2H-dn-3He", "2H-dp-3H", "3H-dn-4He", "3He-dp-4He", "3He-ag-7Be", "3H-ag-7Li", "7Be-np-7Li", "2H-ag-6Li" ] } ], "reactions": [ { "id": "1H-pp-2H", "hasFile": true, "label": "¹H(p,e⁺ν)²H", "updated": null, "kind": "weak", "target": "1H", "projectile": "1H", "ejectile": "e+ nu", "product": "2H", "from": { "code": "1H", "A": 1, "Z": 1, "N": 0 }, "to": { "code": "2H", "A": 2, "Z": 1, "N": 1 }, "networks": [ "pp1" ], "families": [ "pp" ], "importance": "key", "summary": "Two protons fuse into a deuteron, emitting a positron and a neutrino. This is the first and slowest step of the pp chain, and it sets the pace at which the Sun burns hydrogen.", "role": "For two protons to stick together, one of them must turn into a neutron while they are briefly close. That change goes through the weak interaction, the same force behind radioactive β decay, so it happens very rarely: a proton in the centre of the Sun waits billions of years on average before it takes part. This slowness is why the Sun lives so long. Almost every chain that turns hydrogen into helium in the Sun begins here, and the neutrinos it produces, called pp neutrinos, are the most numerous solar neutrinos reaching the Earth.", "details": "The cross section is far too small to measure in the laboratory at any energy, so S(0) is calculated. The calculation needs the overlap of the initial pp scattering state and the deuteron, both well constrained by nucleon-nucleon data, the axial coupling constant from neutron β decay, and two-body (meson-exchange) contributions to the weak axial current, which are fixed in modern calculations by the tritium β-decay rate. Potential-model calculations with several modern nucleon-nucleon interactions (Schiavilla et al. 1998) show a weak model dependence, and the chiral effective field theory calculation of Marcucci et al. (2013) agrees with them. The Solar Fusion evaluations adopt a calculated S(0) whose uncertainty is smaller than that of the measured pp-chain rates, although the reaction has never been observed in the laboratory. The neutrinos it emits are observed directly: Borexino measured the pp-neutrino flux in 2014 (Bellini et al., Nature 512, 383), consistent with the solar-model prediction.", "status": "well-known", "statusNote": "Known from theory only; potential-model and effective-field-theory calculations agree within their small uncertainties.", "statusPlain": "Far too slow ever to be measured in a laboratory, so the rate comes from theory; different calculations agree closely.", "keywords": [], "methods": [ "theory" ], "measurements": [ { "year": 1998, "facility": null, "lab": "", "method": "theory", "energy": "solar energies", "note": "Potential-model calculation with several high-precision nucleon-nucleon interactions, the axial two-body current tuned to the Gamow–Teller matrix element of tritium β decay; the overlap integral Λ²(0) lies between 7.05 and 7.06 for all interactions.", "refs": [ "schiavilla1998" ], "lowestKeV": null, "luna": false }, { "year": 2013, "facility": null, "lab": "", "method": "theory", "energy": "0–100 keV", "note": "Chiral effective field theory with the N3LO two-nucleon potential, full electromagnetic interaction and weak-current constants fixed by the A = 3 binding energies, magnetic moments and tritium β decay; S- and P-wave contributions included. An erratum followed in 2019.", "refs": [ "marcucci2013" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "adelberger2011", "acharya2025" ], "rmatrix": [], "openQuestions": [ "The size of two-body axial-current contributions at higher orders of effective field theory, which dominates the theoretical uncertainty." ], "facts": [], "related": [ "1H-pep-2H", "2H-pg-3He", "3He-hep-4He" ], "q": { "value": 1.4422192329999994, "annihilation": true, "kinetic": 0.42022133299999953 }, "gamow": [ { "network": "pp1", "label": "centre of the Sun", "T9": 0.0157, "E0": 6.087112300027305, "width": 6.627614904602996 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "schiavilla1998", "marcucci2013", "adelberger2011", "acharya2025" ], "luna": false, "lunaYears": [] }, { "id": "1H-pep-2H", "hasFile": true, "label": "¹H(pe⁻,ν)²H", "updated": null, "kind": "weak", "target": "1H", "projectile": "1H e-", "ejectile": "nu", "product": "2H", "from": { "code": "1H", "A": 1, "Z": 1, "N": 0 }, "to": { "code": "2H", "A": 2, "Z": 1, "N": 1 }, "networks": [ "pp1" ], "families": [ "pp" ], "importance": "major", "summary": "Two protons and an electron combine into a deuteron and a neutrino. It is a rare alternative to the fusion of two protons and gives neutrinos of a single, fixed energy.", "role": "In the hot, dense centre of the Sun free electrons are everywhere. Instead of emitting a positron, the fusing pair of protons can absorb one of these electrons. This happens in only a small fraction of the fusions. Because only two particles leave the reaction, the neutrino always carries the same energy, which makes these pep neutrinos a clean probe of the solar core and of how neutrinos change flavour inside the Sun.", "details": "The rate is not measured but calculated relative to the pp reaction: the nuclear matrix element is the same, and the ratio of pep to pp rates depends on the electron density and temperature at the centre of the Sun through a phase-space and electron-wave-function factor. The predicted pep neutrino flux is therefore tied closely to the pp flux and to the solar luminosity. Its monoenergetic line lies in the energy region where the transition between vacuum and matter-enhanced neutrino oscillations takes place. Borexino reported the first evidence of pep neutrinos in 2012 (Bellini et al., Phys. Rev. Lett. 108, 051302): an interaction rate of 3.1 ± 0.6 (stat) ± 0.3 (syst) counts per day per 100 t, which corresponds to a flux of (1.6 ± 0.3) × 10⁸ cm⁻² s⁻¹ for the MSW-LMA oscillation solution, in agreement with the Standard Solar Model. The absence of a pep signal was disfavoured at 98% C.L.", "status": "well-known", "statusNote": "Fixed by the pp rate and the solar electron density; the ratio of the pep to the pp rate is calculated with small uncertainty.", "statusPlain": "", "keywords": [], "methods": [ "theory" ], "measurements": [], "evaluations": [ "adelberger2011", "acharya2025" ], "rmatrix": [], "openQuestions": [], "facts": [], "related": [ "1H-pp-2H" ], "q": { "value": 1.4422192329999994, "annihilation": false, "kinetic": 1.4422192329999994 }, "gamow": [ { "network": "pp1", "label": "centre of the Sun", "T9": 0.0157, "E0": 6.087112300027305, "width": 6.627614904602996 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "adelberger2011", "acharya2025" ], "luna": false, "lunaYears": [] }, { "id": "2H-pg-3He", "hasFile": true, "label": "²H(p,γ)³He", "updated": null, "kind": "capture", "target": "2H", "projectile": "1H", "ejectile": "g", "product": "3He", "from": { "code": "2H", "A": 2, "Z": 1, "N": 1 }, "to": { "code": "3He", "A": 3, "Z": 2, "N": 1 }, "networks": [ "pp1", "bbn" ], "families": [ "pp", "bbn" ], "importance": "key", "summary": "A deuteron captures a proton and becomes ³He, giving off a γ-ray. In the Sun this follows the fusion of two protons almost at once. After the Big Bang it was one of the three reactions that destroyed deuterium, and the one least known before LUNA.", "role": "Deuterium, the nucleus made of one proton and one neutron, was formed in the first minutes after the Big Bang. How much of it survived depends on two things: the density of ordinary matter in the Universe and the speed of the reactions that burn it. This reaction is one of them. Astronomers measure the deuterium left in distant, almost pristine gas clouds; if the burning rate is known, that measurement gives the matter density, which can then be compared with the value from the cosmic microwave background, the light left over from the Big Bang. In stars the reaction is so fast that it never limits the pp chain, but it burns the deuterium of young stars before they start to burn hydrogen.", "details": "Two energy ranges matter. The solar Gamow window lies at a few keV, where the LUNA 50 kV accelerator measured the cross section with about 10% accuracy well below the solar Gamow peak. For Big Bang nucleosynthesis (BBN) the relevant centre-of-mass energies range from tens to a few hundred keV, where before 2020 the data had large uncertainties and an ab initio calculation (Marcucci et al. 2016) predicted an S-factor about 10% above the adopted fits. The capture is dominated by E1 and M1 transitions to the ³He ground state; polarization observables measured at TUNL below 80 keV are sensitive to meson-exchange currents. The LUNA 400 kV measurement with a windowless D₂ gas target and a HPGe detector reached a systematic uncertainty below 3% and settled the rate in the BBN range. With it the BBN-derived baryon density has a 1.6% uncertainty and agrees with the value from the cosmic microwave background (CMB). Measurements at higher energy, with TiD targets, constrain the energy dependence above the BBN window.", "status": "well-known", "statusNote": "Since the LUNA measurement of 2020 the rate at the energies of the Big Bang is known to about 3%. Small differences remain with theoretical calculations and with the data at higher energies.", "statusPlain": "", "keywords": [], "methods": [ "direct-underground", "direct-surface", "theory" ], "measurements": [ { "year": 1997, "facility": null, "lab": "Triangle Universities Nuclear Laboratory, Durham NC", "method": "direct-surface", "energy": "below 80 keV", "note": "Cross sections, S-factors and analyzing powers with polarized and unpolarized beams; the extracted S(0) was about 25% below the value then used in astrophysics, and the vector analyzing power proved sensitive to meson-exchange currents.", "refs": [ "ma1997", "schmid1997" ], "lowestKeV": null, "luna": false }, { "year": 2002, "facility": "luna-50", "lab": "", "method": "direct-underground", "energy": "down to 2.5 keV", "note": "Windowless gas target and segmented 4π BGO detector; first data inside and below the solar Gamow peak, with about 10% accuracy.", "refs": [ "casella2002" ], "lowestKeV": null, "luna": true }, { "year": 2016, "facility": null, "lab": "", "method": "theory", "energy": "BBN range", "note": "Ab initio calculation with the AV18 and Urbana IX interactions and relativistic corrections to the one-body current; S-factor about 10% above the adopted fits.", "refs": [ "marcucci2016" ], "lowestKeV": null, "luna": false }, { "year": 2019, "facility": "jsi-ljubljana", "lab": "", "method": "direct-surface", "energy": "47–210 keV", "note": "Deuterated titanium targets and two HPGe detectors at 90° and 135°; cross sections and angular distributions in good agreement with the ab initio calculation.", "refs": [ "tisma2019" ], "lowestKeV": null, "luna": false }, { "year": 2020, "facility": "luna-400", "lab": "", "method": "direct-underground", "energy": "BBN range", "note": "High-purity D₂ gas target, intense proton beam and a HPGe detector, after a commissioning campaign that brought the systematic uncertainty below 3%. The new rate gives the baryon density to 1.6%, in agreement with the CMB.", "refs": [ "mossa2020b", "mossa2020" ], "lowestKeV": null, "luna": true }, { "year": 2021, "facility": "hzdr", "lab": "", "method": "direct-surface", "energy": "265–1094 keV", "note": "Solid TiD targets, HPGe detectors at 55° and 90°, target deuterium content measured in situ and by elastic recoil detection; the data favour an S-factor higher than earlier fits in this range.", "refs": [ "turkat2021" ], "lowestKeV": null, "luna": false }, { "year": 2024, "facility": "luna-400", "lab": "", "method": "direct-underground", "energy": "energies from 30 to 280 keV", "note": "Angular distribution of the capture γ-rays inferred from the shape of the γ spectrum of a single HPGe detector facing an extended D₂ gas target, and compared with ab initio predictions.", "refs": [ "stockel2024" ], "lowestKeV": null, "luna": true } ], "evaluations": [ "adelberger2011", "acharya2025", "descouvemont2004", "pisanti2021", "fields2020" ], "rmatrix": [], "openQuestions": [ "The residual tension between the measured S-factor and ab initio calculations at a level of a few per cent.", "The energy dependence above the BBN window, where the TiD-target data of 2021 lie above earlier fits." ], "facts": [], "related": [ "1H-pp-2H", "3He-3He2p-4He", "2H-dn-3He", "2H-dp-3H" ], "q": { "value": 5.493475079000003, "annihilation": false, "kinetic": 5.493475079000003 }, "gamow": [ { "network": "pp1", "label": "centre of the Sun", "T9": 0.0157, "E0": 6.699161839222236, "width": 6.952833729241772 }, { "network": "bbn", "label": "deuterium bottleneck", "T9": 0.8, "E0": 92.07619402030879, "width": 184.00111549521745 }, { "network": "bbn", "label": "end of BBN", "T9": 0.3, "E0": 47.88155041745819, "width": 81.25432976630903 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "ma1997", "schmid1997", "casella2002", "marcucci2016", "tisma2019", "mossa2020b", "mossa2020", "turkat2021", "stockel2024", "adelberger2011", "acharya2025", "descouvemont2004", "pisanti2021", "fields2020" ], "luna": true, "lunaYears": [ 2002, 2020, 2024 ] }, { "id": "3He-3He2p-4He", "hasFile": true, "label": "³He(³He,2p)⁴He", "updated": null, "kind": "fusion", "target": "3He", "projectile": "3He", "ejectile": "2 1H", "product": "4He", "from": { "code": "3He", "A": 3, "Z": 2, "N": 1 }, "to": { "code": "4He", "A": 4, "Z": 2, "N": 2 }, "networks": [ "pp1" ], "families": [ "pp" ], "importance": "major", "summary": "Two ³He nuclei fuse into one ⁴He nucleus and release two protons. This closes the main branch of the pp chain in the Sun.", "role": "Once ³He has been made, it can meet another ³He nucleus or a ⁴He nucleus. The first path ends the pp-I chain and produces no further neutrinos; the second opens the pp-II and pp-III branches, which emit the ⁷Be and ⁸B solar neutrinos. The competition between the two therefore sets how many of these neutrinos the Sun emits. In the 1990s the reaction was also measured to test the idea that an unknown low-energy resonance could explain the solar neutrino deficit.", "details": "The two-proton exit channel makes the reaction measurable by detecting the energetic protons in silicon telescopes, which LUNA did with the 50 kV accelerator and a windowless ³He gas target. The data reached below the centre of the solar Gamow peak and excluded a narrow resonance there. The low-energy data show a rise of the S-factor due to electron screening by the atomic electrons of the target, larger than expected; the screening correction is the main uncertainty on the bare-nucleus S(0). Measurements with a doubly charged ³He beam at Osaka, free of molecular-beam contamination, filled the energy gap above the LUNA range. Plasma experiments at laser facilities measured the proton spectrum, whose shape matters when low-resolution detectors are used.", "status": "well-known", "statusNote": "Measured down to the energies at which the reaction runs in the Sun. The remaining uncertainty comes from the correction for the atomic electrons of the target, which make the reaction easier in the laboratory than it is for bare nuclei, and from the energy spectrum of the emitted protons.", "statusPlain": "", "keywords": [], "methods": [ "direct-underground", "direct-surface", "plasma" ], "measurements": [ { "year": 1996, "facility": "luna-50", "lab": "", "method": "direct-underground", "energy": "down to about 21 keV", "note": "First data inside the solar Gamow peak, no evidence for a low-energy resonance; tentative S(0) = 5.1 ± 0.1 MeV b after the screening correction.", "refs": [ "arpesella1996" ], "lowestKeV": null, "luna": true }, { "year": 1998, "facility": "luna-50", "lab": "", "method": "direct-underground", "energy": "down to 20.76 keV", "note": "Full analysis of the first LUNA campaign; electron screening observed clearly for this reaction, larger than expected, and dominating the uncertainty of the bare S(0) = 5.40 MeV b.", "refs": [ "junker1998" ], "lowestKeV": null, "luna": true }, { "year": 1999, "facility": "luna-50", "lab": "", "method": "direct-underground", "energy": "down to 16.5 keV", "note": "New detector setup; data down to the lower edge of the solar Gamow peak, with no sign of the narrow resonance proposed to reduce the ⁷Be and ⁸B neutrino fluxes.", "refs": [ "bonetti1999" ], "lowestKeV": null, "luna": true }, { "year": 2004, "facility": "rcnp-osaka", "lab": "", "method": "direct-surface", "energy": "30–50 keV", "note": "Doubly charged ³He beam free from molecular interference; S-factor in the gap left by LUNA, with smaller statistical and systematic errors than earlier data.", "refs": [ "kudomi2004" ], "lowestKeV": null, "luna": false }, { "year": 2017, "facility": "omega", "lab": "", "method": "plasma", "energy": "low centre-of-mass energy, plasma", "note": "Proton spectra from ³He+³He fusion in high-energy-density plasmas; the measured shape is proposed as a benchmark for the analysis of low-resolution accelerator data.", "refs": [ "zylstra2017" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "adelberger2011", "acharya2025" ], "rmatrix": [], "openQuestions": [ "The origin of the electron-screening enhancement, which is larger than expected.", "The shape of the three-body proton spectrum and its effect on detection efficiencies." ], "facts": [], "related": [ "3He-ag-7Be", "2H-pg-3He", "3He-dp-4He" ], "q": { "value": 12.859579761999997, "annihilation": false, "kinetic": 12.859579761999997 }, "gamow": [ { "network": "pp1", "label": "centre of the Sun", "T9": 0.0157, "E0": 22.103859654761308, "width": 12.629485718264142 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "arpesella1996", "junker1998", "bonetti1999", "kudomi2004", "zylstra2017", "adelberger2011", "acharya2025" ], "luna": true, "lunaYears": [ 1996, 1998, 1999 ] }, { "id": "3He-ag-7Be", "hasFile": true, "label": "³He(α,γ)⁷Be", "updated": null, "kind": "capture", "target": "3He", "projectile": "4He", "ejectile": "g", "product": "7Be", "from": { "code": "3He", "A": 3, "Z": 2, "N": 1 }, "to": { "code": "7Be", "A": 7, "Z": 4, "N": 3 }, "networks": [ "pp2", "pp3", "bbn" ], "families": [ "pp", "bbn" ], "importance": "key", "summary": "A ³He nucleus captures a ⁴He nucleus (an alpha particle) and becomes ⁷Be, giving off a γ-ray. It opens the branches of the pp chain that emit the ⁷Be and ⁸B solar neutrinos, and it made most of the lithium after the Big Bang.", "role": "In the Sun, a ³He nucleus either fuses with another ³He or captures an alpha particle through this reaction. The share that goes this way fixes the number of ⁷Be and ⁸B neutrinos, which detectors such as Borexino and Super-Kamiokande count. It is the largest nuclear uncertainty in the predicted fluxes of those neutrinos. After the Big Bang the ⁷Be made here later decayed to ⁷Li, so the reaction also sets the predicted amount of primordial lithium. That prediction is higher than the amount of lithium seen in old stars, a mismatch called the lithium problem.", "details": "The capture proceeds by external direct capture to the ⁷Be ground state and to its first excited state at 429 keV, so the cross section can be measured either by detecting the prompt γ-rays or by counting the ⁷Be activity afterwards (activation). Before 2006 the two approaches disagreed on the extrapolated S(0). The LUNA campaign at the 400 kV accelerator used a windowless ³He gas target and measured both observables at the same time, down to 93 keV, with agreement between them; the activation results reached a 4% total uncertainty. Surface experiments at the Weizmann Institute, Seattle and Notre Dame, and the ERNA recoil separator, then covered the energies from about 0.3 MeV upwards and constrained the energy dependence needed to extrapolate to the solar Gamow window. Above 1 MeV the ERNA data differ from earlier results in both normalization and slope. Activation measurements at Atomki extended the data to the ⁷Be proton separation threshold and, in 2023, above it, into the region of the known ⁷Be levels. Solar Fusion III recommends S(0) = 0.561 ± 0.018 (exp) ± 0.022 (theory) keV b; the theoretical uncertainty has grown since Solar Fusion II and is now comparable to the experimental one. BBN analyses with the current rates conclude that a nuclear-physics solution of the lithium problem is highly unlikely.", "status": "improving", "statusNote": "Known to a few per cent at solar energies, but only by extending measurements made at higher energies: no experiment has yet reached the energies at which the reaction runs in the Sun.", "statusPlain": "", "keywords": [], "methods": [ "direct-underground", "direct-surface", "activation", "inverse-kinematics" ], "measurements": [ { "year": 2004, "facility": "weizmann", "lab": "", "method": "activation", "energy": "420–950 keV", "note": "Activation with a ³He gas cell; S(0) = 0.53 ± 0.02 ± 0.01 keV b, from a set of energies at a time when earlier activation data covered only one or two energies each.", "refs": [ "narasingh2004" ], "lowestKeV": null, "luna": false }, { "year": 2006, "facility": "luna-400", "lab": "", "method": "activation", "energy": "127, 148 and 169 keV", "note": "Windowless gas target, high beam intensity and low-background γ counting of the ⁷Be produced; cross sections with 4% total uncertainty.", "refs": [ "bemmerer2006" ], "lowestKeV": null, "luna": true }, { "year": 2007, "facility": "luna-400", "lab": "", "method": "activation", "energy": "106 keV", "note": "Activation point at 106 keV, closer to the solar Gamow energy than any earlier measurement; σ = 0.567 ± 0.029 (stat) ± 0.016 (syst) nb.", "refs": [ "gyurky2007" ], "lowestKeV": null, "luna": true }, { "year": 2007, "facility": "luna-400", "lab": "", "method": "direct-underground", "energy": "93, 106 and 170 keV", "note": "Prompt γ-rays and ⁷Be activity measured simultaneously; the two methods agree, branching ratios between the two γ transitions measured to 5–8%, extrapolated S(0) = 0.560 ± 0.017 keV b.", "refs": [ "confortola2007" ], "lowestKeV": null, "luna": true }, { "year": 2007, "facility": "cenpa", "lab": "", "method": "direct-surface", "energy": "0.33–1.23 MeV", "note": "Small gas cell, prompt γ-rays and ⁷Be activity; the two methods agree, and a fit with the Kajino model gives S(0) = 0.595 ± 0.018 keV b.", "refs": [ "brown2007" ], "lowestKeV": null, "luna": false }, { "year": 2008, "facility": "luna-400", "lab": "", "method": "direct-underground", "energy": "beam energies 220, 250 and 400 keV", "note": "Full account of the LUNA prompt-γ experiment and its systematic uncertainties, together with the activation results, and S-factor extrapolations with two theoretical models.", "refs": [ "costantini2008" ], "lowestKeV": null, "luna": true }, { "year": 2009, "facility": "erna", "lab": "", "method": "inverse-kinematics", "energy": "around and above 1 MeV", "note": "Direct detection of the ⁷Be recoils with the ERNA separator, with coincident γ-rays; above 1 MeV the cross section differs from earlier results in absolute value and energy dependence.", "refs": [ "dileva2009" ], "lowestKeV": null, "luna": false }, { "year": 2013, "facility": "notre-dame", "lab": "", "method": "direct-surface", "energy": "about 0.3–1.5 MeV", "note": "Prompt γ-ray measurement with the HIPPO helium-jet gas target over a wide energy window.", "refs": [ "kontos2013" ], "lowestKeV": null, "luna": false }, { "year": 2019, "facility": "atomki", "lab": "", "method": "activation", "energy": "4.0–4.4 MeV", "note": "Thin-window ³He gas cell; a constant cross section of about 10.5 μb near the ⁷Be proton separation threshold and an upper limit of 45 neV on the strength of a resonance there.", "refs": [ "szucs2019" ], "lowestKeV": null, "luna": false }, { "year": 2023, "facility": "atomki", "lab": "", "method": "activation", "energy": "above the ⁷Be proton separation threshold", "note": "Activation with a thin-window ³He gas cell, extending the capture data into the energy range of the known ⁷Be levels, where only one narrow data set (4.0–4.4 MeV) existed before.", "refs": [ "toth2023" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "adelberger2011", "acharya2025", "descouvemont2004", "iliadis2020" ], "rmatrix": [ "7Be" ], "openQuestions": [ "The energy dependence of the S-factor between 100 keV and 1 MeV, which controls the extrapolation to the solar Gamow window.", "The disagreement in slope and normalization above 1 MeV between recoil-separator and γ-ray data." ], "facts": [], "related": [ "3He-3He2p-4He", "7Be-pg-8B", "7Be-ec-7Li", "3H-ag-7Li", "7Be-np-7Li" ], "q": { "value": 1.5871347499999988, "annihilation": false, "kinetic": 1.5871347499999988 }, "gamow": [ { "network": "pp2", "label": "centre of the Sun", "T9": 0.0157, "E0": 23.094476653243145, "width": 12.909388519154763 }, { "network": "bbn", "label": "deuterium bottleneck", "T9": 0.8, "E0": 317.4205317255608, "width": 341.6365154678692 }, { "network": "bbn", "label": "end of BBN", "T9": 0.3, "E0": 165.06532828671817, "width": 150.86564020727639 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": 4598208, "stable": false, "text": "53.2 d" }, "references": [ "narasingh2004", "bemmerer2006", "gyurky2007", "confortola2007", "brown2007", "costantini2008", "dileva2009", "kontos2013", "szucs2019", "toth2023", "adelberger2011", "acharya2025", "descouvemont2004", "iliadis2020" ], "luna": true, "lunaYears": [ 2006, 2007, 2008 ] }, { "id": "7Be-ec-7Li", "hasFile": true, "label": "⁷Be(e⁻,ν)⁷Li", "updated": null, "kind": "decay", "target": "7Be", "projectile": "e-", "ejectile": "nu", "product": "7Li", "from": { "code": "7Be", "A": 7, "Z": 4, "N": 3 }, "to": { "code": "7Li", "A": 7, "Z": 3, "N": 4 }, "networks": [ "pp2" ], "families": [ "pp" ], "importance": "minor", "summary": "⁷Be captures one of the electrons around it and becomes ⁷Li, emitting a neutrino of fixed energy; in the Sun these are the ⁷Be solar neutrinos.", "role": "", "details": "", "status": null, "statusNote": "", "statusPlain": "", "keywords": [], "methods": [], "measurements": [], "evaluations": [], "rmatrix": [], "openQuestions": [], "facts": [], "related": [], "q": { "value": 0.8618950000000005, "annihilation": false, "kinetic": 0.8618950000000005 }, "gamow": [], "thermal": [], "windowNote": "An electron capture: there is no Coulomb barrier to cross, and the rate depends on the density of electrons at the nucleus, which in a star differs from that in a neutral atom.", "halfLife": { "seconds": 4598208, "stable": false, "text": "53.2 d" }, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [], "luna": false, "lunaYears": [] }, { "id": "7Li-pa-4He", "hasFile": true, "label": "⁷Li(p,α)⁴He", "updated": null, "kind": "transfer", "target": "7Li", "projectile": "1H", "ejectile": "4He", "product": "4He", "from": { "code": "7Li", "A": 7, "Z": 3, "N": 4 }, "to": { "code": "4He", "A": 4, "Z": 2, "N": 2 }, "networks": [ "pp2" ], "families": [ "pp" ], "importance": "minor", "summary": "A ⁷Li nucleus captures a proton and splits into two ⁴He nuclei. It is the last step of the pp-II chain, and it destroys lithium in stars.", "role": "The reaction closes the pp-II chain in the Sun but never limits its speed. It matters more as a destroyer of lithium: ⁷Li burns already at temperatures of a few million kelvin, so stars lose their lithium as soon as it is carried deep enough by mixing. The lithium seen at the surface of a star is therefore a clue to how its outer layers mix. After the Big Bang the reaction also removed part of the ⁷Li made directly.", "details": "The cross section is large enough to be measured with good statistics at low energies, which made it a standard case for studying electron screening in laboratory targets: at the lowest energies the measured S-factor rises above the bare-nucleus trend. Engstler et al. (1992) measured it with proton beams on lithium targets and with lithium beams on hydrogen gas, and found the enhancement in all cases. The Trojan Horse method, which is free of screening effects, gave a bare S(0) = 55 ± 3 keV b; compared with the direct data it implies a screening potential of 330 ± 40 eV, well above the adiabatic limit of 175 eV.", "status": "well-known", "statusNote": "Measured down to low energies. The remaining uncertainty is the correction for the atomic electrons of the target, which make the reaction easier in the laboratory than it is for bare nuclei.", "statusPlain": "", "keywords": [], "methods": [ "direct-surface", "thm" ], "measurements": [ { "year": 1992, "facility": null, "lab": "Ruhr-Universität Bochum and Universität Münster", "method": "direct-surface", "energy": "10–1450 keV (whole data set)", "note": "Proton, deuteron and lithium beams with atomic and molecular targets, to compare electron screening in ⁶Li and ⁷Li reactions; the low-energy cross sections are enhanced in all cases, somewhat more for atomic than for molecular targets.", "refs": [ "engstler1992" ], "lowestKeV": null, "luna": false }, { "year": 2001, "facility": null, "lab": "", "method": "thm", "energy": "10–400 keV", "note": "Bare S-factor from the Trojan Horse method in a distorted-wave Born approximation analysis: S_b(0) = 55 ± 3 keV b and a screening potential Uₑ = 330 ± 40 eV, above the adiabatic limit of 175 eV.", "refs": [ "lattuada2001" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "descouvemont2004", "xu2013" ], "rmatrix": [], "openQuestions": [ "The electron-screening potential extracted from low-energy data, which exceeds the atomic-physics estimate." ], "facts": [], "related": [ "7Be-ec-7Li", "3H-ag-7Li", "3He-ag-7Be" ], "q": { "value": 17.346244324, "annihilation": false, "kinetic": 17.346244324 }, "gamow": [ { "network": "pp2", "label": "centre of the Sun", "T9": 0.0157, "E0": 15.254742043300359, "width": 10.49189759346863 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "engstler1992", "lattuada2001", "descouvemont2004", "xu2013" ], "luna": false, "lunaYears": [] }, { "id": "7Be-pg-8B", "hasFile": true, "label": "⁷Be(p,γ)⁸B", "updated": null, "kind": "capture", "target": "7Be", "projectile": "1H", "ejectile": "g", "product": "8B", "from": { "code": "7Be", "A": 7, "Z": 4, "N": 3 }, "to": { "code": "8B", "A": 8, "Z": 5, "N": 3 }, "networks": [ "pp3" ], "families": [ "pp" ], "importance": "key", "summary": "A ⁷Be nucleus captures a proton and becomes ⁸B, giving off a γ-ray. The ⁸B then decays and emits the high-energy solar neutrinos that started the solar neutrino problem.", "role": "Only a small fraction of the ⁷Be in the Sun captures a proton; most of it captures an electron instead. Yet this rare branch makes the most energetic of the common solar neutrinos, the ones seen by the first chlorine detector in the Homestake mine and later measured precisely by Super-Kamiokande and SNO. The predicted number of these neutrinos is directly proportional to the rate of this reaction, so it has to be known well to use them as a probe of the solar core and of neutrino properties.", "details": "The measurement is difficult because the target is radioactive: ⁷Be decays by electron capture, so targets must be produced, characterized and used within months, and their areal density and uniformity become the main systematic uncertainty. The capture is an external, non-resonant E1 process at low energy, with a narrow M1 resonance (the 1⁺ state of ⁸B) near 630 keV, and the extrapolation to solar energies relies on models of the energy dependence. Since 1998 the direct experiments with ⁷Be targets at Orsay and Bordeaux, at the Weizmann Institute and in Seattle give S(0) between about 18.5 and 22 eV b; the Seattle group quotes a model uncertainty of the extrapolation as large as its experimental one. The S-factor has also been inferred from Coulomb dissociation of ⁸B beams on heavy targets, at RIKEN and at GSI. Solar Fusion II based its recommended value on the direct data alone. Solar Fusion III recommends S(0) = 20.5 ± 0.7 eV b, from a halo effective field theory analysis that includes the Coulomb-dissociation data as well as the direct captures.", "status": "improving", "statusNote": "The best direct experiments, all with radioactive ⁷Be targets, differ by up to about 15%; Solar Fusion III, combining them with Coulomb-dissociation data in one theoretical framework, recommends S(0) = 20.5 ± 0.7 eV b (3.4%).", "statusPlain": "", "keywords": [], "methods": [ "direct-surface", "coulomb-dissociation" ], "measurements": [ { "year": 1983, "facility": null, "lab": "Argonne National Laboratory, Argonne IL", "method": "direct-surface", "energy": "low energies and the 1⁺ resonance", "note": "Radioactive ⁷Be target, ⁸B detected through the delayed α particles from its β decay; the ⁷Be areal density determined with two independent methods, which removed the dependence of earlier data on the ⁷Li(d,p)⁸Li normalization.", "refs": [ "filippone1983" ], "lowestKeV": null, "luna": false }, { "year": 1994, "facility": "riken", "lab": "", "method": "coulomb-dissociation", "energy": "⁸B beam at about 50 MeV/u", "note": "First Coulomb-dissociation experiment: break-up of ⁸B into ⁷Be + p in the Coulomb field of a heavy target, converted to the low-energy capture cross section.", "refs": [ "motobayashi1994" ], "lowestKeV": null, "luna": false }, { "year": 1998, "facility": "cenbg", "lab": "", "method": "direct-surface", "energy": "0.35–1.4 MeV", "note": "Two independent measurements with different beam conditions, targets and detectors, in agreement with each other; the extrapolated S(0) is 15–20% below the value recommended at the time.", "refs": [ "hammache1998" ], "lowestKeV": null, "luna": false }, { "year": 2001, "facility": "csnsm-orsay", "lab": "", "method": "direct-surface", "energy": "111.7, 134.7 and 185.8 keV", "note": "A 132 mCi ⁷Be target, intense proton beams and a large-acceptance solenoidal spectrometer; S(0) = 18.5 ± 2.4 eV b from these data and 18.8 ± 1.7 eV b combined with the 1998 results.", "refs": [ "hammache2001" ], "lowestKeV": null, "luna": false }, { "year": 2003, "facility": "weizmann", "lab": "", "method": "direct-surface", "energy": "", "note": "⁷Be implanted in the backing and a raster-scanned proton beam, which removed the loss of ⁸B by backscattering; extrapolated S(0) = 21.2 ± 0.7 eV b in the arXiv version (an erratum followed in 2004).", "refs": [ "baby2003" ], "lowestKeV": null, "luna": false }, { "year": 2003, "facility": "gsi", "lab": "", "method": "coulomb-dissociation", "energy": "⁸B beam at 254 MeV/u", "note": "Exclusive Coulomb-dissociation measurement at high beam energy; the full analysis followed in 2006.", "refs": [ "schumann2003", "schumann2006" ], "lowestKeV": null, "luna": false }, { "year": 2003, "facility": "cenpa", "lab": "", "method": "direct-surface", "energy": "", "note": "Precision measurement with a ⁷Be target made at TRIUMF; S(0) = 22.1 ± 0.6 (expt) ± 0.6 (theor) eV b, and a recommended best value of 21.4 eV b.", "refs": [ "junghans2003" ], "lowestKeV": null, "luna": false }, { "year": 2010, "facility": "cenpa", "lab": "", "method": "direct-surface", "energy": "below the 1⁺ resonance", "note": "Reanalysis of the earlier data with a more detailed target analysis and improved stopping powers: S(0) = 21.5 ± 0.6 (expt) ± 0.6 (theor) eV b, and 20.9 ± 0.6 ± 0.6 eV b from a fit of all modern low-energy data with the same theory.", "refs": [ "junghans2010" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "adelberger2011", "acharya2025" ], "rmatrix": [], "openQuestions": [ "The theoretical energy dependence used to extrapolate the direct data to solar energies.", "The spread of about 15% between the S(0) values of the modern direct experiments." ], "facts": [], "related": [ "3He-ag-7Be", "8B-bp-8Be", "7Be-ec-7Li", "3He-hep-4He" ], "q": { "value": 0.13637106399999865, "annihilation": false, "kinetic": 0.13637106399999865 }, "gamow": [ { "network": "pp3", "label": "centre of the Sun", "T9": 0.0157, "E0": 18.479905962987505, "width": 11.547859396304597 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": 0.7719, "stable": false, "text": "772 ms" }, "references": [ "filippone1983", "motobayashi1994", "hammache1998", "hammache2001", "baby2003", "schumann2003", "schumann2006", "junghans2003", "junghans2010", "adelberger2011", "acharya2025" ], "luna": false, "lunaYears": [] }, { "id": "8B-bp-8Be", "hasFile": true, "label": "⁸B(β⁺ν)⁸Be", "updated": null, "kind": "decay", "target": "8B", "projectile": "", "ejectile": "e+ nu", "product": "8Be", "from": { "code": "8B", "A": 8, "Z": 5, "N": 3 }, "to": { "code": "8Be", "A": 8, "Z": 4, "N": 4 }, "networks": [ "pp3" ], "families": [ "pp" ], "importance": "minor", "summary": "⁸B decays to ⁸Be, which at once breaks into two ⁴He nuclei; the neutrinos of this decay are the high-energy solar neutrinos seen by Homestake, Super-Kamiokande and SNO.", "role": "", "details": "", "status": null, "statusNote": "", "statusPlain": "", "keywords": [], "methods": [], "measurements": [], "evaluations": [], "rmatrix": [], "openQuestions": [], "facts": [], "related": [], "q": { "value": 17.979930000000003, "annihilation": true, "kinetic": 16.957932100000004 }, "gamow": [], "thermal": [], "windowNote": null, "halfLife": { "seconds": 0.7719, "stable": false, "text": "772 ms" }, "productHalfLife": { "seconds": 8.190000000000001e-17, "stable": false, "text": "8.2 × 10⁻¹⁷ s" }, "references": [], "luna": false, "lunaYears": [] }, { "id": "3He-hep-4He", "hasFile": true, "label": "³He(p,e⁺ν)⁴He", "updated": null, "kind": "weak", "target": "3He", "projectile": "1H", "ejectile": "e+ nu", "product": "4He", "from": { "code": "3He", "A": 3, "Z": 2, "N": 1 }, "to": { "code": "4He", "A": 4, "Z": 2, "N": 2 }, "networks": [ "hep" ], "families": [ "pp" ], "importance": "minor", "summary": "A ³He nucleus captures a proton and becomes ⁴He directly, emitting a positron and a neutrino. It is the rarest branch of the pp chain and makes the most energetic solar neutrinos, called hep neutrinos.", "role": "Only a tiny fraction of the pp-chain terminations goes this way, so the reaction adds nothing to the energy of the Sun. Its neutrinos, however, reach higher energies than any other solar neutrinos, beyond the end of the ⁸B spectrum. Large water and scintillator detectors search for them as a test of solar models; so far only upper limits have been set.", "details": "The reaction is a weak capture like p + p, but the leading one-body Gamow–Teller matrix element is strongly suppressed by the symmetries of the ³He and ⁴He wave functions. Two-body axial currents and small components of the wave functions therefore contribute at the same level as the one-body term, and the result is sensitive to cancellations between them. The cross section cannot be measured; the S-factor is taken from ab initio calculations, and the predicted hep flux carries a much larger relative uncertainty than any other solar-neutrino flux. The calculation of Marcucci et al. (2000) with correlated hyperspherical-harmonics wave functions gave an S-factor about 4.5 times the value then used in the standard solar model, with P-wave captures contributing about 40%. On the observational side, the first phase of SNO set an upper limit of 2.3 × 10⁴ cm⁻² s⁻¹ (90% C.L.) on the total hep-neutrino flux (Aharmim et al., Astrophys. J. 653, 1545, 2006).", "status": "unmeasured", "statusNote": "Known only from theory, with large relative uncertainty because of cancellations in the weak matrix element; solar-neutrino detectors give only upper limits on the flux.", "statusPlain": "Known only from theory, and only roughly; solar-neutrino detectors have so far set only upper limits on the neutrinos it makes.", "keywords": [], "methods": [ "theory" ], "measurements": [ { "year": 2000, "facility": null, "lab": "", "method": "theory", "energy": "0–10 keV", "note": "Ab initio calculation with the AV18 two-nucleon and Urbana IX three-nucleon interactions; S(0) = 9.64 × 10⁻²⁰ keV b and 10.1 × 10⁻²⁰ keV b at 10 keV, about 4.5 times the earlier standard value of 2.3 × 10⁻²⁰ keV b. P-wave transitions give about 40% of the result.", "refs": [ "marcucci2000" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "adelberger2011", "acharya2025" ], "rmatrix": [], "openQuestions": [ "A first detection of hep neutrinos, which would test the calculated S-factor.", "The convergence of the two-body current contributions in ab initio calculations." ], "facts": [], "related": [ "1H-pp-2H", "7Be-pg-8B", "3He-3He2p-4He" ], "q": { "value": 19.795274073999998, "annihilation": true, "kinetic": 18.773276174 }, "gamow": [ { "network": "hep", "label": "centre of the Sun", "T9": 0.0157, "E0": 11.058742488143709, "width": 8.933147019479888 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "marcucci2000", "adelberger2011", "acharya2025" ], "luna": false, "lunaYears": [] }, { "id": "12C-pg-13N", "hasFile": true, "label": "¹²C(p,γ)¹³N", "updated": null, "kind": "capture", "target": "12C", "projectile": "1H", "ejectile": "g", "product": "13N", "from": { "code": "12C", "A": 12, "Z": 6, "N": 6 }, "to": { "code": "13N", "A": 13, "Z": 7, "N": 6 }, "networks": [ "cno1" ], "families": [ "cno" ], "importance": "key", "summary": "The first step of the CN cycle. A carbon-12 nucleus captures a proton, emits a γ-ray and becomes radioactive nitrogen-13, which then decays to carbon-13.", "role": "Together with the next proton capture, on carbon-13, this reaction fixes the ratio of the two stable carbon isotopes in gas that has burnt hydrogen. Astronomers measure this ratio in the atmospheres of red giants, where it shows how much material from the burning layers has been mixed to the surface. The same reaction also makes the carbon-13 that, in giant stars, later releases the neutrons needed to build many elements heavier than iron.", "details": "At low energy the capture proceeds by direct E1 capture to the ¹³N ground state, which interferes with the broad resonance at E = 422 keV formed by the first excited state of ¹³N. The S-factor at stellar energies is obtained from R-matrix fits, so the result depends on the normalization of the data and on the width of that resonance. Measurements since 2023, prompt-γ and activation, give S-factors about 25% lower than most of the earlier literature. The LUNA data reach E = 60 keV, where the cross section enters the energy range of hydrogen burning in the shells of giant stars.", "status": "improving", "statusNote": "Direct data now reach 60 keV with systematic uncertainties of 7–8%; the remaining question is the normalization difference of about 25% with respect to the older data sets.", "statusPlain": "Measured underground down to low energies with an uncertainty under 10%; the older measurements differ from the new ones by about a quarter overall, and why is still an open question.", "keywords": [], "methods": [ "direct-underground", "direct-surface", "activation" ], "measurements": [ { "year": 1974, "facility": null, "lab": "", "method": "direct-surface", "energy": "about 150 keV to 2.5 MeV (proton energy)", "note": "Showed that direct E1 capture to the ground state, interfering with the resonances at proton energies of 457 and 1699 keV, is needed to describe the excitation function; ground-state spectroscopic factor C²S = 0.49 ± 0.15.", "refs": [ "rolfs1974" ], "lowestKeV": null, "luna": false }, { "year": 2023, "facility": "atomki", "lab": "", "method": "activation", "energy": "300–1900 keV (proton energy)", "note": "Total cross section from the ¹³N activity, with uncertainties independent of in-beam γ-ray spectroscopy; covers the region of the 1.7 MeV resonance, where earlier data were scarce.", "refs": [ "gyurky2023" ], "lowestKeV": null, "luna": false }, { "year": 2023, "facility": "felsenkeller", "lab": "", "method": "direct-underground", "energy": "320–620 keV", "note": "Shallow-underground measurement across the 422 keV resonance; S-factor about 25% below the literature. The R-matrix fit gives the first excited state of ¹³N at 2369.6(4) keV with Γγ = 0.49(3) eV and Γp = 34.9(2) keV.", "refs": [ "skowronski2023b" ], "lowestKeV": null, "luna": false }, { "year": 2023, "facility": "notre-dame", "lab": "", "method": "direct-surface", "energy": "1.0–2.5 MeV (proton energy)", "note": "Absolute cross section over a wide energy range to fix the overall normalization and the interference between overlapping resonances; the extrapolation to low energy uses a Bayesian uncertainty analysis.", "refs": [ "kettner2023" ], "lowestKeV": null, "luna": false }, { "year": 2023, "facility": "luna-400", "lab": "", "method": "direct-underground", "energy": "down to 60 keV", "note": "Prompt γ-ray detection and activation, with overall systematic uncertainties of 7–8%; the S-factor is about 25% lower than most earlier data.", "refs": [ "skowronski2023" ], "lowestKeV": null, "luna": true } ], "evaluations": [ "xu2013", "acharya2025" ], "rmatrix": [ "13N" ], "openQuestions": [ "The 25% normalization difference between the measurements since 2023 and the older data sets.", "The radiative width of the 422 keV resonance, which dominates the rate at higher temperatures." ], "facts": [ { "text": "However long hydrogen burns in a giant star, carbon-12 cannot fall below about 3.6 times carbon-13: this floor, 3.6 ± 0.4, follows from the ratio of the two carbon proton-capture rates measured underground.", "refs": [ "skowronski2023" ] }, { "text": "The same data can give different error bars: a 2025 study fitted this reaction with several frequentist and Bayesian R-matrix methods and found that how systematic uncertainties and their correlations are handled decides how reliable the final uncertainty is.", "refs": [ "skowronski2025b" ] } ], "related": [ "13N-bp-13C", "13C-pg-14N", "14N-pg-15O" ], "q": { "value": 1.9434910639999998, "annihilation": false, "kinetic": 1.9434910639999998 }, "gamow": [ { "network": "cno1", "label": "centre of the Sun", "T9": 0.0157, "E0": 24.651744960737698, "width": 13.337531002176696 }, { "network": "cno1", "label": "core of a 15 M☉ star", "T9": 0.035, "E0": 42.068780939279335, "width": 26.014517094949962 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": 597.9, "stable": false, "text": "9.96 min" }, "references": [ "rolfs1974", "gyurky2023", "skowronski2023b", "kettner2023", "skowronski2023", "xu2013", "acharya2025", "skowronski2025b" ], "luna": true, "lunaYears": [ 2023 ] }, { "id": "13N-bp-13C", "hasFile": true, "label": "¹³N(β⁺ν)¹³C", "updated": null, "kind": "decay", "target": "13N", "projectile": "", "ejectile": "e+ nu", "product": "13C", "from": { "code": "13N", "A": 13, "Z": 7, "N": 6 }, "to": { "code": "13C", "A": 13, "Z": 6, "N": 7 }, "networks": [ "cno1" ], "families": [ "cno" ], "importance": "minor", "summary": "The radioactive nitrogen-13 made by proton capture on carbon-12 turns into stable carbon-13 by emitting a positron and a neutrino.", "role": "", "details": "", "status": null, "statusNote": "", "statusPlain": "", "keywords": [], "methods": [], "measurements": [], "evaluations": [], "rmatrix": [], "openQuestions": [], "facts": [], "related": [], "q": { "value": 2.2204707000000004, "annihilation": true, "kinetic": 1.1984728000000004 }, "gamow": [], "thermal": [], "windowNote": null, "halfLife": { "seconds": 597.9, "stable": false, "text": "9.96 min" }, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [], "luna": false, "lunaYears": [] }, { "id": "13C-pg-14N", "hasFile": true, "label": "¹³C(p,γ)¹⁴N", "updated": null, "kind": "capture", "target": "13C", "projectile": "1H", "ejectile": "g", "product": "14N", "from": { "code": "13C", "A": 13, "Z": 6, "N": 7 }, "to": { "code": "14N", "A": 14, "Z": 7, "N": 7 }, "networks": [ "cno1" ], "families": [ "cno" ], "importance": "key", "summary": "Carbon-13 captures a proton, emits a γ-ray and becomes nitrogen-14. It is the step of the CN cycle that destroys carbon-13.", "role": "The balance between this reaction, which destroys carbon-13, and the capture on carbon-12, which makes it, sets the ratio of the two carbon isotopes left behind by hydrogen burning. That ratio is measured in red giants, in planetary nebulae and in meteoritic grains, and is used to test how material is mixed inside stars. The rate also controls how much carbon-13 survives to act as a neutron source in giant stars.", "details": "Below 1 MeV the cross section is the sum of direct capture and of two resonances, a 2⁻ state and a 1⁻ state in ¹⁴N observed at proton energies of about 448 and 551 keV. Capture populates the ground state and several excited states of ¹⁴N, so the total S-factor at low energy rests on R-matrix fits of the individual transitions. For a long time a single data set reported all transitions. The LUNA measurement extended the data down to E = 60 keV and, together with the later Felsenkeller data, gives S-factors 20–30% lower than the earlier literature.", "status": "improving", "statusNote": "Underground data now reach 60 keV with 7–8% systematic uncertainty; the rate is lower than in the compilations based on the 1994 data, and the resonance parameters have been revised.", "statusPlain": "Measured underground down to low energies with an uncertainty under 10%; the rate came out lower than in the older tables.", "keywords": [], "methods": [ "direct-underground", "direct-surface", "anc" ], "measurements": [ { "year": 1994, "facility": null, "lab": "", "method": "direct-surface", "energy": "120–950 keV (proton energy)", "note": "Cross sections for capture to the first six states of ¹⁴N, most of them for the first time; resonances at Ep = 450.4 and 557.6 ± 0.5 keV; total S-factor extrapolated to 25 keV of 7.7 ± 1.0 keV b.", "refs": [ "king1994" ], "lowestKeV": null, "luna": false }, { "year": 2023, "facility": "luna-400", "lab": "", "method": "direct-underground", "energy": "down to 60 keV", "note": "Prompt γ-ray detection with overall systematic uncertainties of 7–8%; the S-factor is about 30% lower than most earlier data.", "refs": [ "skowronski2023" ], "lowestKeV": null, "luna": true }, { "year": 2025, "facility": "felsenkeller", "lab": "", "method": "direct-underground", "energy": "310–680 keV (Ep = 330–740 keV)", "note": "Shallow-underground measurement in direct kinematics. The S-factor agrees with LUNA at low energy and is about 20% below the earlier literature over the whole range; new parameters for the two resonances and S_tot(0) = 6.4(4) keV b.", "refs": [ "skowronski2025" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "xu2013", "acharya2025" ], "rmatrix": [ "14N" ], "openQuestions": [ "The branching of the capture to the excited states of ¹⁴N below 300 keV, where only the LUNA data exist.", "The cause of the 20–30% difference between the recent data and the 1994 data set." ], "facts": [], "related": [ "12C-pg-13N", "13N-bp-13C", "14N-pg-15O" ], "q": { "value": 7.550563564000001, "annihilation": false, "kinetic": 7.550563564000001 }, "gamow": [ { "network": "cno1", "label": "centre of the Sun", "T9": 0.0157, "E0": 24.701067056131034, "width": 13.350866899180993 }, { "network": "cno1", "label": "core of a 15 M☉ star", "T9": 0.035, "E0": 42.15295025183199, "width": 26.040528424973353 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "king1994", "skowronski2023", "skowronski2025", "xu2013", "acharya2025" ], "luna": true, "lunaYears": [ 2023 ] }, { "id": "14N-pg-15O", "hasFile": true, "label": "¹⁴N(p,γ)¹⁵O", "updated": null, "kind": "capture", "target": "14N", "projectile": "1H", "ejectile": "g", "product": "15O", "from": { "code": "14N", "A": 14, "Z": 7, "N": 7 }, "to": { "code": "15O", "A": 15, "Z": 8, "N": 7 }, "networks": [ "cno1" ], "families": [ "cno" ], "importance": "key", "summary": "The slowest step of the CNO cycle. Its rate decides how fast the cycle runs, how much energy it gives, and how many CNO neutrinos leave the Sun.", "role": "In a star burning hydrogen through the CNO cycle, nuclei wait longest as ¹⁴N before they capture the next proton. This one reaction therefore sets the pace of the whole cycle. It controls the energy production of stars more massive than the Sun, the flux of CNO neutrinos from the Sun's core, and, through the lifetime of stars leaving the main sequence, the ages estimated for the oldest star clusters.", "details": "At solar temperatures the Gamow window lies near 27 keV, where the cross section is far too small to measure, so the S-factor is extrapolated from higher energies with R-matrix fits. The capture proceeds mainly to the 6.79 MeV excited state of ¹⁵O and to its ground state, which makes the extrapolation sensitive to the γ-ray summing. Capture into the 6.79 MeV state carries most of the low-energy S-factor. As a subthreshold resonance, the state also shapes the ground-state transition, and that contribution scales with its radiative width, i.e. with the inverse of its lifetime; it has been probed through the lifetime and through asymptotic normalization coefficients from transfer reactions. The LUNA measurements at the 400 kV accelerator under Gran Sasso extended the data down to 70 keV, much closer to the solar energies than any surface experiment, and gave a total S(0) near 1.7 keV b; Solar Fusion III recommends S(0) = 1.68 ± 0.14 keV b, an uncertainty of 8.4%. A 2025 measurement at Ep = 110–260 keV with the 350 kV accelerator in Hefei determined all transitions together in a multichannel Bayesian analysis and reports S(0) = 1.92 ± 0.08 keV b, about 14% above the Solar Fusion III value (Chen et al. 2025); the two have not yet been reconciled. The rate matters for the Sun because Borexino's measurement of the CNO neutrino flux can be turned into the carbon and nitrogen content of the solar core only through it (Borexino 2023). Surface measurements at HZDR and Notre Dame since 2018 cover 0.3–1.3 MeV with high precision and anchor the R-matrix fit above the underground data, and an activation measurement at Atomki gives the total cross section at 0.55–1.4 MeV independently of γ-ray spectroscopy. A new LUNA campaign with solid nitrogen targets and a 4π BGO detector aims at the total and partial cross sections at about 100–370 keV, for a rate with 5% precision (Gosta et al. 2025; Compagnucci et al. 2025).", "status": "improving", "statusNote": "Direct data reach 70 keV; the remaining uncertainty comes from the split into the individual γ-ray transitions and from the extrapolation to solar energies. Solar Fusion III recommends S(0) = 1.68 ± 0.14 keV b; a 2025 measurement finds 1.92 ± 0.08 keV b.", "statusPlain": "Measured underground close to the energies of the Sun. What remains uncertain is how the reaction divides among its several ways of giving off γ-rays, and the last step down to solar energies; a 2025 measurement finds a rate about 14% above the recommended one.", "keywords": [], "methods": [ "direct-underground", "direct-surface", "activation", "lifetime", "anc" ], "measurements": [ { "year": 2001, "facility": null, "lab": "Triangle Universities Nuclear Laboratory, Durham NC", "method": "lifetime", "energy": "259 keV resonance (Doppler-shift attenuation)", "note": "Mean lifetime of the 6793 keV state of ¹⁵O, τ ≈ 1.6 fs (90% C.L.), from the Doppler-shift attenuation method. The value implies a much smaller contribution of the subthreshold state to the ground-state transition than inferred from the (p,γ) data.", "refs": [ "bertone2001" ], "lowestKeV": null, "luna": false }, { "year": 2003, "facility": "texas-am", "lab": "", "method": "anc", "energy": "proton-transfer reactions", "note": "Asymptotic normalization coefficients for ¹⁴N + p → ¹⁵O from proton-transfer reactions, which fix the normalization of the direct capture to the ¹⁵O states and constrain the S-factor at zero energy.", "refs": [ "mukhamedzhanov2003" ], "lowestKeV": null, "luna": false }, { "year": 2004, "facility": "luna-400", "lab": "", "method": "direct-underground", "energy": "140–400 keV (proton energy)", "note": "First underground measurement with a solid TiN target and a HPGe detector, separating the γ-ray transitions; total S(0) = 1.7 ± 0.2 keV b from an R-matrix analysis.", "refs": [ "formicola2004" ], "lowestKeV": null, "luna": true }, { "year": 2005, "facility": null, "lab": "Triangle Universities Nuclear Laboratory, Durham NC", "method": "direct-surface", "energy": "155–524 keV (proton energy)", "note": "Direct measurement of the individual transitions at the surface; the extrapolated total S(0) is close to 1.7 keV b, in agreement with the LUNA result.", "refs": [ "runkle2005" ], "lowestKeV": null, "luna": false }, { "year": 2005, "facility": "luna-400", "lab": "", "method": "direct-underground", "energy": "119–367 keV (effective)", "note": "Full account of the LUNA solid-target campaign with TiN targets and HPGe detectors. Because of the level structure of ¹⁵O, the extrapolated S(0) depends on the R-matrix model.", "refs": [ "imbriani2005" ], "lowestKeV": null, "luna": true }, { "year": 2006, "facility": "luna-400", "lab": "", "method": "direct-underground", "energy": "down to 70 keV", "note": "Windowless nitrogen gas target and 4π BGO summing detector; the cross section was measured down to 70 keV, where it is 0.24 pb.", "refs": [ "lemut2006" ], "lowestKeV": null, "luna": true }, { "year": 2008, "facility": null, "lab": "", "method": "lifetime", "energy": "278 keV resonance (proton energy; Doppler-shift attenuation)", "note": "New Doppler-shift attenuation measurement of the 6792 keV state at the same resonance: the finite lifetime reported in 2001 is not confirmed, and τ < 0.77 fs.", "refs": [ "schurmann2008" ], "lowestKeV": null, "luna": false }, { "year": 2011, "facility": "luna-400", "lab": "", "method": "direct-underground", "energy": "proton energies 359, 380 and 399 keV", "note": "A composite germanium detector reduced the summing corrections; new cross sections for capture to the ground state and to the 5181, 6172 and 6792 keV states.", "refs": [ "marta2011" ], "lowestKeV": null, "luna": true }, { "year": 2018, "facility": "hzdr", "lab": "", "method": "direct-surface", "energy": "0.357–1.292 MeV", "note": "S-factors at twelve energies for capture to the 6.79 MeV state, the strongest transition, and at ten energies between 0.479 and 1.202 MeV for the second strongest; the total rate uncertainty remained about 8%.", "refs": [ "wagner2018" ], "lowestKeV": null, "luna": false }, { "year": 2021, "facility": "notre-dame", "lab": "", "method": "lifetime", "energy": "Doppler-shift attenuation", "note": "Lifetimes of several excited states of ¹⁵O; τ = 0.6 ± 0.4 fs for the 6792 keV state, below the 2001 value and consistent with the 2008 limit.", "refs": [ "frentz2021" ], "lowestKeV": null, "luna": false }, { "year": 2022, "facility": "atomki", "lab": "", "method": "activation", "energy": "550–1400 keV", "note": "Total cross section from the ¹⁵O activity, counted through the annihilation radiation of its β⁺ decay, with about 10% uncertainty and no dependence on γ-ray angular distributions or summing.", "refs": [ "gyurky2022" ], "lowestKeV": null, "luna": false }, { "year": 2022, "facility": "notre-dame", "lab": "", "method": "direct-surface", "energy": "0.27–1.07 MeV (proton energy)", "note": "New data in an energy range where few measurements existed, analysed with a multichannel R-matrix fit of the ground-state and 6.79 MeV transitions; differences between the data and the R-matrix fits remain.", "refs": [ "frentz2022" ], "lowestKeV": null, "luna": false }, { "year": 2025, "facility": "luna-400", "lab": "", "method": "direct-underground", "energy": "about 100–370 keV (campaign under way)", "note": "Description of a new LUNA campaign with solid nitrogen targets and a 4π BGO detector, which aims at total and partial cross sections for a rate with 5% precision; no cross sections published yet.", "refs": [ "gosta2025", "compagnucci2025" ], "lowestKeV": null, "luna": true }, { "year": 2025, "facility": null, "lab": "350 kV accelerator, Hefei", "method": "direct-surface", "energy": "Eₚ = 110–260 keV", "note": "All transitions measured at once and their S-factors determined together in a multichannel Bayesian analysis of the γ spectra; S(0) = 1.92 ± 0.08 keV b, about 14% above the Solar Fusion III recommendation. The authors discuss what the higher value means for the tension between Borexino's CNO neutrinos and the low-metallicity solar composition.", "refs": [ "chen2025" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "adelberger2011", "xu2013", "acharya2025" ], "rmatrix": [], "openQuestions": [ "The ground-state transition, whose contribution at low energy depends on interference in the R-matrix fit.", "The lifetime of the 6.79 MeV state of ¹⁵O, for which the published values disagree.", "The total S(0), where the 2025 value of 1.92 ± 0.08 keV b and the Solar Fusion III recommendation of 1.68 ± 0.14 keV b differ by about 14%." ], "facts": [], "related": [ "13C-pg-14N", "15O-bp-15N", "15N-pa-12C", "15N-pg-16O", "12C-pg-13N" ], "q": { "value": 7.296787864, "annihilation": false, "kinetic": 7.296787864 }, "gamow": [ { "network": "cno1", "label": "centre of the Sun", "T9": 0.0157, "E0": 27.421564715290582, "width": 14.066878140623823 }, { "network": "cno1", "label": "core of a 15 M☉ star", "T9": 0.035, "E0": 46.795543311726284, "width": 27.43709025321959 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": 122.266, "stable": false, "text": "2.04 min" }, "references": [ "bertone2001", "mukhamedzhanov2003", "formicola2004", "runkle2005", "imbriani2005", "lemut2006", "schurmann2008", "marta2011", "wagner2018", "frentz2021", "gyurky2022", "frentz2022", "gosta2025", "compagnucci2025", "chen2025", "adelberger2011", "xu2013", "acharya2025", "borexino2020", "borexino2023" ], "luna": true, "lunaYears": [ 2004, 2005, 2006, 2011, 2025 ] }, { "id": "15O-bp-15N", "hasFile": true, "label": "¹⁵O(β⁺ν)¹⁵N", "updated": null, "kind": "decay", "target": "15O", "projectile": "", "ejectile": "e+ nu", "product": "15N", "from": { "code": "15O", "A": 15, "Z": 8, "N": 7 }, "to": { "code": "15N", "A": 15, "Z": 7, "N": 8 }, "networks": [ "cno1" ], "families": [ "cno" ], "importance": "minor", "summary": "Oxygen-15 turns into nitrogen-15 by emitting a positron and a neutrino; these neutrinos are part of the solar CNO neutrino flux.", "role": "", "details": "", "status": null, "statusNote": "", "statusPlain": "", "keywords": [], "methods": [], "measurements": [], "evaluations": [], "rmatrix": [], "openQuestions": [], "facts": [], "related": [], "q": { "value": 2.7541618999999997, "annihilation": true, "kinetic": 1.7321639999999998 }, "gamow": [], "thermal": [], "windowNote": null, "halfLife": { "seconds": 122.266, "stable": false, "text": "2.04 min" }, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [], "luna": false, "lunaYears": [] }, { "id": "15N-pa-12C", "hasFile": true, "label": "¹⁵N(p,α)¹²C", "updated": null, "kind": "transfer", "target": "15N", "projectile": "1H", "ejectile": "4He", "product": "12C", "from": { "code": "15N", "A": 15, "Z": 7, "N": 8 }, "to": { "code": "12C", "A": 12, "Z": 6, "N": 6 }, "networks": [ "cno1" ], "families": [ "cno" ], "importance": "key", "summary": "The last step of the CN cycle. Nitrogen-15 captures a proton and splits into carbon-12 and a helium nucleus, so the carbon that started the cycle comes back.", "role": "A proton that hits nitrogen-15 can either knock out a helium nucleus, which closes the CN cycle, or stay and make oxygen-16, which opens the second CNO cycle. The first outcome is by far the more frequent. The ratio between the two decides how much material leaks from the CN cycle into the cycles that run through oxygen and fluorine, and so how much oxygen-16 hydrogen burning makes.", "details": "The (p,α) channel competes with ¹⁵N(p,γ)¹⁶O through the same ¹⁶O compound states; at low energy both are dominated by the tails of two broad 1⁻ resonances, whose interference fixes the energy dependence of the S-factor. The cross section is large compared with the other CN-cycle reactions, so it never limits the cycle speed; what matters for nucleosynthesis is the ratio to the (p,γ) channel. The direct data of 1982 reach a proton energy of 80 keV. Trojan-Horse data extend the S-factor down to about 20 keV without Coulomb suppression or electron screening, and agree with the direct data where they overlap. R-matrix fits give S(0) = 73 ± 5 MeV b from the direct data and 70 ± 13.5 MeV b from the Trojan-Horse data.", "status": "well-known", "statusNote": "Direct measurements and the indirect Trojan Horse method agree, with uncertainties of 7% and 19%. The reaction is fast, and its remaining uncertainty does not limit models of the CN cycle.", "statusPlain": "", "keywords": [], "methods": [ "direct-surface", "thm" ], "measurements": [ { "year": 1982, "facility": null, "lab": "", "method": "direct-surface", "energy": "80–810 keV (proton energy)", "note": "Cross section of the α₀ channel measured with a 350 kV implanter and a 1 MV accelerator, normalized at Ep = 353.4 keV. For decades this was the main direct data set at low energy and the basis of the recommended S(0).", "refs": [ "redder1982" ], "lowestKeV": null, "luna": false }, { "year": 2007, "facility": null, "lab": "", "method": "thm", "energy": "about 20–312 keV", "note": "Bare-nucleus cross section from the quasi-free ²H(¹⁵N,α¹²C)n reaction at 60 MeV beam energy; agrees with the direct data between 70 and 312 keV and extends the S-factor to about 20 keV.", "refs": [ "lacognata2007" ], "lowestKeV": null, "luna": false }, { "year": 2009, "facility": null, "lab": "", "method": "thm", "energy": "R-matrix reanalysis", "note": "R-matrix fits of the direct and Trojan-Horse data, including the finite energy resolution of the latter: S(0) = 73.0 ± 5.0 MeV b from the direct data, adopted by Solar Fusion II, and 70.0 ± 13.5 MeV b from the Trojan-Horse data.", "refs": [ "lacognata2009" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "adelberger2011", "xu2013", "acharya2025" ], "rmatrix": [], "openQuestions": [ "The electron-screening correction needed to compare direct data at the lowest energies with Trojan-Horse results." ], "facts": [], "related": [ "15N-pg-16O", "12C-pg-13N", "14N-pg-15O" ], "q": { "value": 4.965493294, "annihilation": false, "kinetic": 4.965493294 }, "gamow": [ { "network": "cno1", "label": "centre of the Sun", "T9": 0.0157, "E0": 27.46247759085584, "width": 14.07736809504133 }, { "network": "cno1", "label": "core of a 15 M☉ star", "T9": 0.035, "E0": 46.865362093418696, "width": 27.457550644162634 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "redder1982", "lacognata2007", "lacognata2009", "adelberger2011", "xu2013", "acharya2025" ], "luna": false, "lunaYears": [] }, { "id": "15N-pg-16O", "hasFile": true, "label": "¹⁵N(p,γ)¹⁶O", "updated": null, "kind": "capture", "target": "15N", "projectile": "1H", "ejectile": "g", "product": "16O", "from": { "code": "15N", "A": 15, "Z": 7, "N": 8 }, "to": { "code": "16O", "A": 16, "Z": 8, "N": 8 }, "networks": [ "cno2" ], "families": [ "cno" ], "importance": "key", "summary": "The branch point of the CNO cycles. Rarely, nitrogen-15 keeps the captured proton and becomes oxygen-16, and the material passes from the first CNO cycle into the second.", "role": "Every time this reaction happens instead of the much more frequent ¹⁵N(p,α)¹²C, a nucleus leaves the CN cycle and enters the cycle that runs through oxygen and fluorine. Its rate therefore sets how much oxygen-16, oxygen-17 and fluorine hydrogen burning produces in red giants, in AGB stars and in nova explosions. Measurements deep underground at Gran Sasso, by the LUNA collaboration, showed that the rate is about half the value used in the older compilations.", "details": "The capture at low energy is dominated by the two broad 1⁻ resonances in ¹⁶O that also govern ¹⁵N(p,α)¹²C, interfering with each other and with direct capture to the ¹⁶O ground state. The non-resonant contribution and the interference sign between the resonances determine the S-factor below the first resonance. Asymptotic normalization coefficients (ANCs) from transfer reactions constrain the direct-capture component. The LUNA data, from 70 to 370 keV, and the Notre Dame data, from 130 keV to 1.8 MeV, give a rate about a factor of 2 below the NACRE and CF88 compilations, with an uncertainty near 10%.", "status": "improving", "statusNote": "Measurements deep underground reach 70 keV and fix the rate to about 10%. The remaining uncertainty is in extending the data to lower energies, where several contributions to the reaction interfere with each other.", "statusPlain": "", "keywords": [], "methods": [ "direct-underground", "direct-surface", "anc" ], "measurements": [ { "year": 2008, "facility": null, "lab": "", "method": "anc", "energy": "transfer reactions; R-matrix fit", "note": "Asymptotic normalization coefficients for ¹⁵N + p → ¹⁶O fix the direct capture to the ¹⁶O ground state. The R-matrix fit gives about one CN catalyst lost to the second cycle every 2200 ± 300 cycles, instead of about 1000 in the NACRE compilation.", "refs": [ "mukhamedzhanov2008" ], "lowestKeV": null, "luna": false }, { "year": 2009, "facility": "luna-400", "lab": "", "method": "direct-underground", "energy": "90–230 keV", "note": "Total cross section with a windowless nitrogen gas target and a 4π BGO summing detector; the cross section at nova energies is a factor of 2 lower than previously believed.", "refs": [ "bemmerer2009" ], "lowestKeV": null, "luna": true }, { "year": 2010, "facility": "notre-dame", "lab": "", "method": "direct-surface", "energy": "130–1800 keV (proton energy)", "note": "Measurement across both broad resonances, at Ep = 338 and 1028 keV, and below them; a multilevel R-matrix analysis gives S(0) = 39.6 keV b.", "refs": [ "leblanc2010" ], "lowestKeV": null, "luna": false }, { "year": 2011, "facility": "luna-400", "lab": "", "method": "direct-underground", "energy": "70–370 keV", "note": "Extends the LUNA data and confirms the earlier R-matrix extrapolation. The rate is about a factor of 2 below NACRE and CF88, with a 10% uncertainty.", "refs": [ "caciolli2011" ], "lowestKeV": null, "luna": true }, { "year": 2012, "facility": "notre-dame", "lab": "", "method": "direct-surface", "energy": "", "note": "Exclusive cross sections for the γ-ray cascades through excited states of ¹⁶O, measured together with ¹⁵N(p,α₁γ)¹²C.", "refs": [ "imbriani2012" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "adelberger2011", "xu2013", "acharya2025" ], "rmatrix": [], "openQuestions": [ "The direct-capture contribution to the ground state, which sets the S-factor below the lower resonance." ], "facts": [], "related": [ "15N-pa-12C", "16O-pg-17F", "14N-pg-15O" ], "q": { "value": 12.127411264, "annihilation": false, "kinetic": 12.127411264 }, "gamow": [ { "network": "cno2", "label": "core of a 15 M☉ star", "T9": 0.035, "E0": 46.865362093418696, "width": 27.457550644162634 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "mukhamedzhanov2008", "bemmerer2009", "leblanc2010", "caciolli2011", "imbriani2012", "adelberger2011", "xu2013", "acharya2025" ], "luna": true, "lunaYears": [ 2009, 2011 ] }, { "id": "16O-pg-17F", "hasFile": true, "label": "¹⁶O(p,γ)¹⁷F", "updated": null, "kind": "capture", "target": "16O", "projectile": "1H", "ejectile": "g", "product": "17F", "from": { "code": "16O", "A": 16, "Z": 8, "N": 8 }, "to": { "code": "17F", "A": 17, "Z": 9, "N": 8 }, "networks": [ "cno2" ], "families": [ "cno" ], "importance": "major", "summary": "Oxygen-16 captures a proton and becomes radioactive fluorine-17. It is the slowest step of the second CNO cycle.", "role": "Because this capture is slow, most of the oxygen-16 in a star survives hydrogen burning. The small part that burns makes oxygen-17, whose amount relative to oxygen-16 is measured in red giants and in grains of stardust found in meteorites, and is used to test stellar models.", "details": "There are no resonances at stellar energies. The cross section is direct capture to the ¹⁷F ground state and to its first excited state, a weakly bound 1/2⁺ level whose extended wave function makes the capture to it dominant at low energy and gives the S-factor a steep rise towards zero energy. The energy dependence is therefore well described by direct-capture and microscopic models, and the rate rests on surface data scaled with such a model. Solar Fusion II adopts S(0) = 10.6 ± 0.8 keV b from model calculations normalized to the data of 1973 and 1997. A 2008 evaluation, which corrected the data sets since 1958 for coincidence summing and stopping powers, gives the rate with an uncertainty of about 7%. A Bayesian fit of all reliable data, with a potential model whose scaling parameters are the asymptotic normalization coefficients of the two bound states, halves that uncertainty to ±4.2% (Iliadis et al. 2022).", "status": "well-known", "statusNote": "A non-resonant direct-capture reaction whose energy dependence is fixed by theory; a Bayesian analysis (2022) gives the rate to ±4.2%, about half the earlier 7%, limited by the normalization of the surface data.", "statusPlain": "Known to about 4%: how the cross section changes with energy is well understood from theory, and the remaining uncertainty is in the overall scale of the measurements.", "keywords": [], "methods": [ "direct-surface", "theory" ], "measurements": [ { "year": 1997, "facility": null, "lab": "", "method": "direct-surface", "energy": "", "note": "Cross sections for capture to the ground state and to the first excited state. The S-factor for the excited-state transition rises as the energy decreases, which the authors explained by the loose binding of the proton in the 1/2⁺ state.", "refs": [ "morlock1997" ], "lowestKeV": null, "luna": false }, { "year": 2022, "facility": null, "lab": "", "method": "theory", "energy": "all reliable data sets, refitted", "note": "All reliable cross sections fitted with a single-particle potential model, the ANCs of the ¹⁷F ground and first excited states used as scaling parameters, with statistical and systematic uncertainties treated separately; the rate uncertainty is ±4.2%, about half of the previously reported 7.5%.", "refs": [ "iliadis2022" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "adelberger2011", "iliadis2008", "acharya2025", "iliadis2022" ], "rmatrix": [ "17F" ], "openQuestions": [ "Direct data closer to the Gamow window, to test the predicted rise of the S-factor at low energy." ], "facts": [], "related": [ "17F-bp-17O", "15N-pg-16O", "17O-pa-14N" ], "q": { "value": 0.6002689640000003, "annihilation": false, "kinetic": 0.6002689640000003 }, "gamow": [ { "network": "cno2", "label": "core of a 15 M☉ star", "T9": 0.035, "E0": 51.295732864964826, "width": 28.726083886812557 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": 64.37, "stable": false, "text": "1.07 min" }, "references": [ "morlock1997", "iliadis2022", "adelberger2011", "iliadis2008", "acharya2025" ], "luna": false, "lunaYears": [] }, { "id": "17F-bp-17O", "hasFile": true, "label": "¹⁷F(β⁺ν)¹⁷O", "updated": null, "kind": "decay", "target": "17F", "projectile": "", "ejectile": "e+ nu", "product": "17O", "from": { "code": "17F", "A": 17, "Z": 9, "N": 8 }, "to": { "code": "17O", "A": 17, "Z": 8, "N": 9 }, "networks": [ "cno2" ], "families": [ "cno" ], "importance": "minor", "summary": "Fluorine-17 turns into stable oxygen-17 by emitting a positron and a neutrino.", "role": "", "details": "", "status": null, "statusNote": "", "statusPlain": "", "keywords": [], "methods": [], "measurements": [], "evaluations": [], "rmatrix": [], "openQuestions": [], "facts": [], "related": [], "q": { "value": 2.7604642, "annihilation": true, "kinetic": 1.7384663 }, "gamow": [], "thermal": [], "windowNote": null, "halfLife": { "seconds": 64.37, "stable": false, "text": "1.07 min" }, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [], "luna": false, "lunaYears": [] }, { "id": "17O-pa-14N", "hasFile": true, "label": "¹⁷O(p,α)¹⁴N", "updated": null, "kind": "transfer", "target": "17O", "projectile": "1H", "ejectile": "4He", "product": "14N", "from": { "code": "17O", "A": 17, "Z": 8, "N": 9 }, "to": { "code": "14N", "A": 14, "Z": 7, "N": 7 }, "networks": [ "cno2" ], "families": [ "cno" ], "importance": "key", "summary": "Oxygen-17 captures a proton and splits into nitrogen-14 and a helium nucleus. This closes the second CNO cycle and destroys oxygen-17.", "role": "The amount of oxygen-17 that a star makes and later shows at its surface depends on how fast this reaction destroys it. Astronomers compare the ratio of oxygen-17 to oxygen-16 in red giants and in grains of stardust found in meteorites with stellar models, and this reaction is one of the main nuclear inputs to that comparison. In nova explosions it competes with ¹⁷O(p,γ)¹⁸F, which makes the radioactive fluorine-18.", "details": "At the temperatures of red giants and AGB stars the rate is dominated by a narrow resonance at E = 64.5 keV (the ¹⁸F state at Ex = 5672 keV), whose strength is too small to measure at the surface. At nova temperatures the resonance at E = 183 keV dominates. It was reported as a new resonance in 2005, and its (p,α) strength, 1.6–1.7 meV, now agrees between several experiments. LUNA measured the 64.5 keV resonance directly underground: ωγ = 10.0 ± 1.4 (stat) ± 0.7 (syst) neV, which gives a proton width of 35 ± 5 ± 3 neV, about twice the earlier values, and doubles the rate at red-giant and AGB temperatures. The Trojan-Horse determinations of the same resonance give a lower strength.", "status": "improving", "statusNote": "At nova temperatures the rate is well measured. In red giants and AGB stars it depends on a single very weak resonance at 64.5 keV, an energy at which the reaction is strongly favoured; there the underground measurement and the indirect Trojan Horse method differ by about a factor of 3.", "statusPlain": "", "keywords": [], "methods": [ "direct-underground", "direct-surface", "inverse-kinematics", "thm" ], "measurements": [ { "year": 2005, "facility": "csnsm-orsay", "lab": "", "method": "direct-surface", "energy": "around Ep = 194 keV", "note": "Discovery of the resonance at E_R(lab) = 194.1 ± 0.6 keV in the (p,α) channel, with strength 1.6 ± 0.2 meV; the (p,γ) channel was measured by activation in the same experiment.", "refs": [ "chafa2005" ], "lowestKeV": null, "luna": false }, { "year": 2007, "facility": null, "lab": "Holifield Radioactive Ion Beam Facility, Oak Ridge", "method": "inverse-kinematics", "energy": "183 keV resonance", "note": "Heavy-ion ¹⁷O beam on a windowless hydrogen gas target, with α and ¹⁴N detected in coincidence by silicon strip detectors inside the gas: E_R = 183.5 (+0.1/−0.4) keV and ωγ = 1.70 ± 0.15 meV.", "refs": [ "moazen2007" ], "lowestKeV": null, "luna": false }, { "year": 2010, "facility": null, "lab": "", "method": "thm", "energy": "0–300 keV", "note": "Indirect measurement of the bare-nucleus cross section; both the 65 keV and the 183 keV resonances are observed and the strength of the 65 keV resonance is extracted.", "refs": [ "sergi2010" ], "lowestKeV": null, "luna": false }, { "year": 2015, "facility": "luna-400", "lab": "", "method": "direct-underground", "energy": "Ep = 194.8 keV resonance", "note": "Commissioning of a silicon-detector setup for α particles underground: ωγ = 1.68 ± 0.03 (stat) ± 0.12 (syst) meV and Ep = 194.8 ± 0.3 keV, the most precise resonance energy so far. Underground the background near 200 keV was up to a factor of 15 lower than at the surface.", "refs": [ "bruno2015" ], "lowestKeV": null, "luna": true }, { "year": 2015, "facility": null, "lab": "", "method": "thm", "energy": "65 and 183 keV resonances", "note": "Improved Trojan-Horse analysis of narrow-resonance strengths; the 65 keV strength was used to renormalize the same resonance in the (p,γ) channel.", "refs": [ "sergi2015" ], "lowestKeV": null, "luna": false }, { "year": 2016, "facility": "luna-400", "lab": "", "method": "direct-underground", "energy": "64.5 keV resonance", "note": "Direct measurement of the 64.5 keV resonance: ωγ = 10.0 ± 1.4 (stat) ± 0.7 (syst) neV and Γp = 35 ± 5 (stat) ± 3 (syst) neV, about twice the earlier values, which doubles the rate at red-giant and AGB temperatures and lowers the predicted ¹⁷O/¹⁶O ratio.", "refs": [ "bruno2016" ], "lowestKeV": null, "luna": true } ], "evaluations": [ "adelberger2011", "acharya2025" ], "rmatrix": [], "openQuestions": [ "The difference of about a factor of 3 between the LUNA and Trojan-Horse strengths of the 64.5 keV resonance.", "The subthreshold state of ¹⁸F, whose contribution at solar energies Solar Fusion II discusses together with the 65 keV resonance." ], "facts": [ { "text": "Stars may destroy oxygen-17 faster than the standard tables say: a 2025 LUNA analysis finds the rates up to twice the tabulated ones below about 100 million kelvin, with the dominant (p,α) channel known within 20% (95% confidence).", "refs": [ "rapagnani2025" ] } ], "related": [ "17O-pg-18F", "16O-pg-17F", "17F-bp-17O", "14N-pg-15O" ], "q": { "value": 1.1918741940000004, "annihilation": false, "kinetic": 1.1918741940000004 }, "gamow": [ { "network": "cno2", "label": "core of a 15 M☉ star", "T9": 0.035, "E0": 51.3557454740199, "width": 28.742882782357054 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "chafa2005", "moazen2007", "sergi2010", "bruno2015", "sergi2015", "bruno2016", "adelberger2011", "acharya2025", "rapagnani2025" ], "luna": true, "lunaYears": [ 2015, 2016 ] }, { "id": "17O-pg-18F", "hasFile": true, "label": "¹⁷O(p,γ)¹⁸F", "updated": null, "kind": "capture", "target": "17O", "projectile": "1H", "ejectile": "g", "product": "18F", "from": { "code": "17O", "A": 17, "Z": 8, "N": 9 }, "to": { "code": "18F", "A": 18, "Z": 9, "N": 9 }, "networks": [ "cno3" ], "families": [ "cno" ], "importance": "key", "summary": "Oxygen-17 captures a proton and becomes radioactive fluorine-18. It opens the third CNO cycle.", "role": "In nova explosions this reaction makes fluorine-18. When fluorine-18 decays it emits positrons, and their annihilation produces γ-rays that space telescopes could detect in the first hours after the explosion. The rate also sets, together with ¹⁷O(p,α)¹⁴N, how much oxygen-17 and oxygen-18 a nova ejects, which is compared with the isotope ratios of presolar grains thought to come from novae.", "details": "At nova temperatures the rate is dominated by the resonance at E = 183 keV together with the non-resonant direct-capture contribution; at lower temperatures the narrow resonance at 64.5 keV also contributes. The 183 keV resonance strength and the direct-capture S-factor have been measured with prompt-γ, activation and recoil-separator techniques; the γ-ray decay of the resonance proceeds through many cascades, which makes efficiency and angular corrections important. The LUNA measurements at Gran Sasso gave ωγ(183 keV) = 1.67 ± 0.12 µeV and reduced the rate uncertainty at nova temperatures by a factor of 4; the lower background revealed γ-ray transitions missed at the surface. In 2024 LUNA also measured the 64.5 keV resonance directly, ωγ = 30 ± 6 (stat) ± 2 (syst) peV, about twice the value adopted from indirect data.", "status": "improving", "statusNote": "The nova-relevant resonance is measured directly to about 7%; at lower temperatures the 64.5 keV resonance, measured directly only once, and the direct-capture component dominate the uncertainty.", "statusPlain": "Well measured at the temperatures of nova explosions; at the lower temperatures of ordinary stars it depends on a very weak resonance measured directly only once.", "keywords": [], "methods": [ "direct-underground", "direct-surface", "inverse-kinematics", "activation" ], "measurements": [ { "year": 2005, "facility": "tunl-lena", "lab": "", "method": "direct-surface", "energy": "140–540 keV (proton energy)", "note": "Proton beams of up to 100 µA on tantalum backings anodised in ¹⁷O-enriched water; new thermonuclear rate including the 183 keV resonance.", "refs": [ "fox2005" ], "lowestKeV": null, "luna": false }, { "year": 2005, "facility": "csnsm-orsay", "lab": "", "method": "activation", "energy": "around Ep = 194 keV", "note": "The (p,γ) channel of the 183 keV resonance measured by ¹⁸F activation, together with the (p,α) channel.", "refs": [ "chafa2005" ], "lowestKeV": null, "luna": false }, { "year": 2012, "facility": "dragon", "lab": "", "method": "inverse-kinematics", "energy": "250–500 keV", "note": "S-factor measured in inverse kinematics with the DRAGON recoil separator, which detects the ¹⁸F recoils directly.", "refs": [ "hager2012" ], "lowestKeV": null, "luna": false }, { "year": 2012, "facility": "notre-dame", "lab": "", "method": "direct-surface", "energy": "", "note": "The primary γ-ray transitions were used in an R-matrix analysis to estimate the direct-capture contribution; the new rate combines these data with earlier S-factor determinations.", "refs": [ "kontos2012" ], "lowestKeV": null, "luna": false }, { "year": 2012, "facility": "luna-400", "lab": "", "method": "direct-underground", "energy": "200–370 keV", "note": "First direct measurement in the Gamow window of classical novae; ωγ(183 keV) = 1.67 ± 0.12 µeV, the most precise value then, and a rate uncertainty reduced by a factor of 4.", "refs": [ "scott2012" ], "lowestKeV": null, "luna": true }, { "year": 2014, "facility": "luna-400", "lab": "", "method": "direct-underground", "energy": "nova Gamow window", "note": "Full analysis of the LUNA campaign with prompt γ-ray detection and activation; recommended rate with which the oxygen and fluorine isotopes ejected by novae are predicted to about 10%.", "refs": [ "dileva2014" ], "lowestKeV": null, "luna": true }, { "year": 2015, "facility": "tunl-lena", "lab": "", "method": "direct-surface", "energy": "170–530 keV (proton energy)", "note": "Beam currents up to 2 mA; ωγ = (1.86 ± 0.13) µeV for the resonance at Ep = 193 keV and (13.70 ± 0.96) meV at 518 keV, and a direct-capture S(0) = 4.82 ± 0.41 keV b.", "refs": [ "buckner2015" ], "lowestKeV": null, "luna": false }, { "year": 2024, "facility": "luna-400", "lab": "", "method": "direct-underground", "energy": "64.5 keV resonance", "note": "First direct measurement of the 64.5 keV resonance, the lowest strength ever measured directly: ωγ = 30 ± 6 (stat) ± 2 (syst) peV. The proton width, 34 ± 7 ± 3 neV, agrees with the LUNA result from the (p,α) channel.", "refs": [ "gesue2024" ], "lowestKeV": 64.5, "luna": true } ], "evaluations": [ "acharya2025" ], "rmatrix": [], "openQuestions": [ "The direct-capture S-factor between the low-energy resonances.", "The strength of the 64.5 keV resonance, where the direct result is about twice the value from indirect data." ], "facts": [], "related": [ "17O-pa-14N", "18F-bp-18O", "18O-pa-15N" ], "q": { "value": 5.607106864, "annihilation": false, "kinetic": 5.607106864 }, "gamow": [ { "network": "cno3", "label": "AGB star", "T9": 0.05, "E0": 65.14138845550961, "width": 38.6914753721059 }, { "network": "cno3", "label": "classical nova", "T9": 0.2, "E0": 164.14601306895085, "width": 122.83777741576517 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": 6584.04, "stable": false, "text": "1.83 h" }, "references": [ "fox2005", "chafa2005", "hager2012", "kontos2012", "scott2012", "dileva2014", "buckner2015", "gesue2024", "acharya2025" ], "luna": true, "lunaYears": [ 2012, 2014, 2024 ] }, { "id": "18F-bp-18O", "hasFile": true, "label": "¹⁸F(β⁺ν)¹⁸O", "updated": null, "kind": "decay", "target": "18F", "projectile": "", "ejectile": "e+ nu", "product": "18O", "from": { "code": "18F", "A": 18, "Z": 9, "N": 9 }, "to": { "code": "18O", "A": 18, "Z": 8, "N": 10 }, "networks": [ "cno3", "he-burning" ], "families": [ "cno", "he" ], "importance": "minor", "summary": "Fluorine-18 turns into stable oxygen-18 by emitting a positron and a neutrino; in nova explosions the annihilation of these positrons gives a γ-ray signal.", "role": "", "details": "", "status": null, "statusNote": "", "statusPlain": "", "keywords": [], "methods": [], "measurements": [], "evaluations": [], "rmatrix": [], "openQuestions": [], "facts": [], "related": [], "q": { "value": 1.6559163, "annihilation": true, "kinetic": 0.6339184 }, "gamow": [], "thermal": [], "windowNote": null, "halfLife": { "seconds": 6584.04, "stable": false, "text": "1.83 h" }, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [], "luna": false, "lunaYears": [] }, { "id": "18O-pa-15N", "hasFile": true, "label": "¹⁸O(p,α)¹⁵N", "updated": null, "kind": "transfer", "target": "18O", "projectile": "1H", "ejectile": "4He", "product": "15N", "from": { "code": "18O", "A": 18, "Z": 8, "N": 10 }, "to": { "code": "15N", "A": 15, "Z": 7, "N": 8 }, "networks": [ "cno3" ], "families": [ "cno" ], "importance": "key", "summary": "Oxygen-18 captures a proton and splits into nitrogen-15 and a helium nucleus. It closes the third CNO cycle and destroys oxygen-18.", "role": "This reaction removes oxygen-18 in hydrogen-burning layers, and so it shapes the oxygen isotope ratios that astronomers measure in giant stars and in grains of stardust. The nitrogen-15 it produces is also a step on the way to fluorine in AGB stars, where nitrogen-15 can capture a helium nucleus.", "details": "The rate at stellar temperatures is the sum of several low-energy resonances in ¹⁹F, at E = 20, 90 and 143 keV, and of non-resonant contributions from the tails of broad higher-lying states. The 20 keV resonance is far below the reach of direct measurements, and its strength comes from Trojan-Horse data. LUNA measured the cross section underground down to E = 55 keV, where it is below 1 pb/sr, and found the 90 keV resonance about ten times stronger than previously reported. A multichannel R-matrix fit of these and earlier data gives the rate between 0.01 and 1 GK.", "status": "improving", "statusNote": "Direct data now reach 55 keV; the 20 keV resonance, which matters at the lowest temperatures, is known only from Trojan-Horse data.", "statusPlain": "Measured directly down to low energies; a resonance that matters in the coolest environments is known only from an indirect method.", "keywords": [], "methods": [ "direct-surface", "direct-underground", "thm" ], "measurements": [ { "year": 2008, "facility": null, "lab": "", "method": "thm", "energy": "20 and 90 keV resonances", "note": "First experimental evaluation of the 20 keV resonance, whose contribution came out about 35% larger than previously estimated; the 90 keV resonance appeared negligible. The rate accuracy improved by a factor of 8.5 because it rests on a measured strength.", "refs": [ "lacognata2008" ], "lowestKeV": null, "luna": false }, { "year": 2015, "facility": "luna-400", "lab": "", "method": "direct-underground", "energy": "Ep = 151 keV resonance", "note": "Commissioning of a silicon-detector setup for α particles underground: ωγ = 164.2 ± 0.9 (stat) +12.1/−11.7 (syst) meV and a new resonance energy Ep = 151.2 ± 0.3 keV.", "refs": [ "bruno2015" ], "lowestKeV": null, "luna": true }, { "year": 2019, "facility": "luna-400", "lab": "", "method": "direct-underground", "energy": "55–340 keV", "note": "Cross section measured down to 55 keV, the lowest energy so far. The 90 keV resonance is a factor of 10 stronger than previously reported; the multichannel R-matrix rate is more precise than earlier evaluations between 0.01 and 1 GK.", "refs": [ "bruno2019" ], "lowestKeV": 55, "luna": true } ], "evaluations": [ "acharya2025" ], "rmatrix": [], "openQuestions": [ "The strength of the 20 keV resonance, known only from Trojan-Horse data.", "The 90 keV resonance, whose direct LUNA strength is ten times the earlier value, while the Trojan-Horse analysis found it negligible." ], "facts": [], "related": [ "18O-pg-19F", "17O-pg-18F", "18F-bp-18O", "15N-pa-12C" ], "q": { "value": 3.9798007939999995, "annihilation": false, "kinetic": 3.9798007939999995 }, "gamow": [ { "network": "cno3", "label": "AGB star", "T9": 0.05, "E0": 65.20905001647891, "width": 38.711564337301084 }, { "network": "cno3", "label": "classical nova", "T9": 0.2, "E0": 164.3165095188188, "width": 122.90155590473275 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "lacognata2008", "bruno2015", "bruno2019", "acharya2025" ], "luna": true, "lunaYears": [ 2015, 2019 ] }, { "id": "18O-pg-19F", "hasFile": true, "label": "¹⁸O(p,γ)¹⁹F", "updated": null, "kind": "capture", "target": "18O", "projectile": "1H", "ejectile": "g", "product": "19F", "from": { "code": "18O", "A": 18, "Z": 8, "N": 10 }, "to": { "code": "19F", "A": 19, "Z": 9, "N": 10 }, "networks": [ "cno4" ], "families": [ "cno" ], "importance": "major", "summary": "Oxygen-18 captures a proton and keeps it, becoming fluorine-19. This opens the fourth CNO cycle.", "role": "Most protons that hit oxygen-18 produce a helium nucleus and nitrogen-15 instead. The small fraction that makes fluorine-19 decides how much material passes into the last CNO cycle and towards neon. The rate also enters the oxygen isotope ratios predicted for giant stars and novae.", "details": "The same ¹⁹F states govern ¹⁸O(p,γ)¹⁹F and ¹⁸O(p,α)¹⁵N, so the two reactions share resonance energies and total widths and differ in the partial widths. At stellar energies the γ-ray channel is weak compared with the α channel. The low-energy cross section is the sum of direct capture, the tail of the strong resonance at E = 143 keV, the resonance at 90 keV and, at the lowest temperatures, a resonance at 20 keV known only from indirect data. LUNA measured the 90 keV resonance directly for the first time, with a 4π BGO summing detector deep underground: its strength, 0.53 ± 0.07 neV, is too small to matter for the stellar rate. Solar Fusion III adopts a direct-capture S(0) = 23 ± 3.8 keV b.", "status": "improving", "statusNote": "Direct data reach 85 keV and rule out a large 90 keV contribution; the direct-capture component and the 20 keV resonance still need study.", "statusPlain": "Measured directly down to low energies, which ruled out a large contribution once thought possible; the lowest-energy part still needs study.", "keywords": [], "methods": [ "direct-underground", "direct-surface" ], "measurements": [ { "year": 2012, "facility": "tunl-lena", "lab": "", "method": "direct-surface", "energy": "95 keV resonance (proton energy)", "note": "Intense beams from an electron-cyclotron-resonance ion source and γγ-coincidence detection on anodised tantalum targets enriched to 99.3% in ¹⁸O; a new upper limit for the strength of the 95 keV resonance and rates for cool bottom processing in low-mass AGB stars.", "refs": [ "buckner2012" ], "lowestKeV": null, "luna": false }, { "year": 2019, "facility": "luna-400", "lab": "", "method": "direct-underground", "energy": "85–140 keV", "note": "First direct measurement in this energy range, with a 4π BGO summing detector. The 90 keV resonance has ωγ = 0.53 ± 0.07 neV, three orders of magnitude below the indirect estimate and a factor of 20 below the previous upper limit, so it does not contribute significantly to the stellar rate.", "refs": [ "best2019" ], "lowestKeV": null, "luna": true }, { "year": 2021, "facility": "luna-400", "lab": "", "method": "direct-underground", "energy": "resonances at 151, 215, 274 and 334 keV (proton energy)", "note": "Second LUNA campaign, with a HPGe detector, on the higher-energy resonances; it confirmed the contributions of these resonances to the stellar rate.", "refs": [ "pantaleo2021" ], "lowestKeV": null, "luna": true } ], "evaluations": [ "acharya2025" ], "rmatrix": [], "openQuestions": [ "The direct-capture S-factor at low energy, which Solar Fusion III flags for further study.", "The strength of the 20 keV resonance, known only from indirect data." ], "facts": [], "related": [ "18O-pa-15N", "19F-pa-16O", "19F-pg-20Ne" ], "q": { "value": 7.993599864, "annihilation": false, "kinetic": 7.993599864 }, "gamow": [ { "network": "cno4", "label": "AGB star", "T9": 0.05, "E0": 65.20905001647891, "width": 38.711564337301084 }, { "network": "cno4", "label": "classical nova", "T9": 0.2, "E0": 164.3165095188188, "width": 122.90155590473275 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "buckner2012", "best2019", "pantaleo2021", "acharya2025" ], "luna": true, "lunaYears": [ 2019, 2021 ] }, { "id": "19F-pa-16O", "hasFile": true, "label": "¹⁹F(p,α)¹⁶O", "updated": null, "kind": "transfer", "target": "19F", "projectile": "1H", "ejectile": "4He", "product": "16O", "from": { "code": "19F", "A": 19, "Z": 9, "N": 10 }, "to": { "code": "16O", "A": 16, "Z": 8, "N": 8 }, "networks": [ "cno4" ], "families": [ "cno" ], "importance": "key", "summary": "Fluorine-19 captures a proton and splits into oxygen-16 and a helium nucleus. It is the main way stars destroy fluorine during hydrogen burning.", "role": "Fluorine is the most fragile of the light elements made in stars, and its origin is still debated. In AGB stars, which are thought to make much of the fluorine in the Galaxy, part of the fluorine produced can be destroyed by this reaction if it is mixed into hot hydrogen-burning layers. The reaction also returns material to oxygen-16 and closes the fourth CNO cycle.", "details": "The reaction proceeds through states of ²⁰Ne and has several α channels: to the ¹⁶O ground state, emitting α particles, and to excited ¹⁶O states, followed by γ-ray (and pair) emission. At low energy each channel must be measured separately. For the α₀ channel, direct data reach 0.2 MeV and give S-factors 1.5–2 times larger than the adopted extrapolations, and Trojan-Horse data, which reach lower energies, show resonances that direct measurements had not seen. Between 0.4 and 0.9 MeV, measurements with the LHASA silicon-strip array (2023, 2025) give an α₀ S-factor about 1.4 times the NACRE value at 0.6–0.8 MeV and resolve the disagreement between the two earlier data sets there. The (p,αγ) channel was measured deep underground at JUNA across the whole Gamow window, from E = 72 to 344 keV.", "status": "uncertain", "statusNote": "The part of the reaction that leaves oxygen excited, so that it emits a γ-ray, has now been measured underground at stellar energies. The main part, which leaves oxygen in its ground state, is known below 200 keV only from the indirect Trojan Horse method.", "statusPlain": "", "keywords": [], "methods": [ "direct-underground", "direct-surface", "thm" ], "measurements": [ { "year": 2011, "facility": null, "lab": "", "method": "thm", "energy": "below about 300 keV (α₀ channel)", "note": "First study of the α₀ channel at astrophysical energies, from the quasi-free parts of ²H(¹⁹F,α¹⁶O)n and ¹⁹F(³He,α¹⁶O)d. Resonances not observed before raise the rate at astrophysical temperatures by up to a factor of 1.7.", "refs": [ "lacognata2011" ], "lowestKeV": null, "luna": false }, { "year": 2015, "facility": null, "lab": "", "method": "direct-surface", "energy": "0.2–0.6 MeV (α₀ channel)", "note": "Direct measurement at deeply sub-Coulomb energies; the S-factor is 1.5–2 times larger than the extrapolations then adopted.", "refs": [ "lombardo2015" ], "lowestKeV": null, "luna": false }, { "year": 2017, "facility": null, "lab": "", "method": "thm", "energy": "about 0–1 MeV (α₀ channel)", "note": "Improved Trojan-Horse measurement of the α₀ S-factor over the energy range of astrophysical interest.", "refs": [ "indelicato2017" ], "lowestKeV": null, "luna": false }, { "year": 2021, "facility": "juna", "lab": "", "method": "direct-underground", "energy": "72.4–344 keV", "note": "First measurement of the (p,αγ) channel in the low-energy part of the Gamow window (70–200 keV), at the China JinPing Underground Laboratory.", "refs": [ "zhang2021" ], "lowestKeV": null, "luna": false }, { "year": 2023, "facility": null, "lab": "", "method": "direct-surface", "energy": "E_cm = 0.4–0.9 MeV (α₀ channel)", "note": "Direct measurement with the LHASA silicon-strip array; the S-factor is about 1.4 times the NACRE value in the 0.6–0.8 MeV region, confirming the trend of the latest data. A fuller account with angular distributions followed in 2025 and resolves the discrepancy between the two earlier data sets.", "refs": [ "guardo2023", "petruse2025" ], "lowestKeV": null, "luna": false } ], "evaluations": [], "rmatrix": [], "openQuestions": [ "The contribution of low-energy resonances to the separate α channels.", "The ratio to ¹⁹F(p,γ)²⁰Ne, which decides how much material leaks from the CNO cycles towards neon." ], "facts": [], "related": [ "19F-pg-20Ne", "18O-pg-19F", "15N-pa-12C" ], "q": { "value": 8.113612194, "annihilation": false, "kinetic": 8.113612194 }, "gamow": [ { "network": "cno4", "label": "AGB star", "T9": 0.05, "E0": 70.60148685497924, "width": 40.28039387140643 }, { "network": "cno4", "label": "classical nova", "T9": 0.2, "E0": 177.9045988849291, "width": 127.88227921032797 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "lacognata2011", "lombardo2015", "indelicato2017", "zhang2021", "guardo2023", "petruse2025" ], "luna": false, "lunaYears": [] }, { "id": "19F-pg-20Ne", "hasFile": true, "label": "¹⁹F(p,γ)²⁰Ne", "updated": null, "kind": "capture", "target": "19F", "projectile": "1H", "ejectile": "g", "product": "20Ne", "from": { "code": "19F", "A": 19, "Z": 9, "N": 10 }, "to": { "code": "20Ne", "A": 20, "Z": 10, "N": 10 }, "networks": [ "cno4" ], "families": [ "cno" ], "importance": "key", "summary": "Fluorine-19 captures a proton and keeps it, becoming neon-20. This is the way out of the CNO cycles towards heavier elements.", "role": "In all the CNO cycles the catalyst nuclei carbon, nitrogen, oxygen and fluorine are recycled, so their total number stays the same. This reaction is the exception: it carries material out of the cycles into neon, from which the NeNa and MgAl cycles can build heavier nuclei. Its rate, compared with the much more frequent ¹⁹F(p,α)¹⁶O, sets how fast this leakage happens in very hot hydrogen burning, as in massive stars without heavy elements and in nova explosions.", "details": "The γ-ray channel is weak compared with the α channels of the same ²⁰Ne states, so measurements at low energy need intense beams and low-background detection, which motivated underground experiments. The rate at the relevant temperatures depends on low-energy resonances and on the non-resonant contribution, and on the γ-ray branchings of the ²⁰Ne states near the proton threshold. A surface measurement in 2008 observed only the transition to the first excited state of ²⁰Ne and gave an upper limit for the resonance near 213 keV. The JUNA experiment, deep under the JinPing mountain, reached E = 186 keV and identified a key resonance at 225 keV; near 0.1 GK its rate is up to 7.4 times the previous recommendation. Before the JUNA result, an R-matrix analysis fitted the (p,γ), (p,α) and (p,p) data together (deBoer et al. 2021). It found the rate uncertainty considerably larger than previously reported. The causes are unresolved interferences, possible threshold and subthreshold states and direct capture. A Gamow shell model calculation gives, near 0.1 GK, a rate close to the JUNA one (Dong et al. 2024, preprint). A ¹⁹F + p measurement is under way at the LUNA 400 kV accelerator.", "status": "uncertain", "statusNote": "Underground data now reach 186 keV; below that the rate depends on weak resonances not yet measured directly, and on the (p,γ)/(p,α) ratio.", "statusPlain": "Measured underground down to fairly low energies. Below them the rate depends on weak resonances not yet seen directly, and on how often this reaction wins over its competitor ¹⁹F(p,α)¹⁶O.", "keywords": [], "methods": [ "direct-underground", "direct-surface" ], "measurements": [ { "year": 2008, "facility": "notre-dame", "lab": "", "method": "direct-surface", "energy": "200–760 keV", "note": "Resonances at 323.9, 564 and 634 keV and interference terms between them; only an upper limit for the expected resonance at 213 keV. Only the transition to the first excited state of ²⁰Ne was measured.", "refs": [ "couture2008" ], "lowestKeV": null, "luna": false }, { "year": 2022, "facility": "juna", "lab": "", "method": "direct-underground", "energy": "down to 186 keV", "note": "Direct measurement at the China JinPing Underground Laboratory; a key resonance at 225 keV raises the rate near 0.1 GK by up to a factor of 7.4. Stellar models then give a stronger breakout from the CNO cycle in first stars, a possible source of the calcium seen in the most iron-poor stars.", "refs": [ "zhang2022" ], "lowestKeV": 186, "luna": false } ], "evaluations": [ "acharya2025" ], "rmatrix": [], "openQuestions": [ "The strength of the lowest-energy resonances and the non-resonant contribution.", "The leakage ratio (p,γ)/(p,α) at the temperatures of hot hydrogen burning." ], "facts": [], "related": [ "19F-pa-16O", "18O-pg-19F", "20Ne-pg-21Na" ], "q": { "value": 12.843458164, "annihilation": false, "kinetic": 12.843458164 }, "gamow": [ { "network": "cno4", "label": "AGB star", "T9": 0.05, "E0": 70.60148685497924, "width": 40.28039387140643 }, { "network": "cno4", "label": "classical nova", "T9": 0.2, "E0": 177.9045988849291, "width": 127.88227921032797 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "couture2008", "zhang2022", "acharya2025", "deboer2021", "dong2024" ], "luna": false, "lunaYears": [] }, { "id": "20Ne-pg-21Na", "hasFile": true, "label": "²⁰Ne(p,γ)²¹Na", "updated": null, "kind": "capture", "target": "20Ne", "projectile": "1H", "ejectile": "g", "product": "21Na", "from": { "code": "20Ne", "A": 20, "Z": 10, "N": 10 }, "to": { "code": "21Na", "A": 21, "Z": 11, "N": 10 }, "networks": [ "nena" ], "families": [ "nena" ], "importance": "key", "summary": "The first and slowest step of the NeNa cycle. A ²⁰Ne nucleus captures a proton and becomes ²¹Na, giving off the extra energy as a γ-ray.", "role": "²⁰Ne is the most abundant neon isotope, and in the NeNa cycle nuclei wait longest as ²⁰Ne before the next proton arrives. This reaction therefore sets how fast neon is turned into sodium in the hydrogen-burning layers of red giants, of massive stars on the asymptotic giant branch (AGB stars, in the late stage where hydrogen and helium burn in thin shells), and in nova explosions. Because so much neon is available, even a slow leak through this step matters for the sodium made in these stars.", "details": "Below about 0.4 MeV the cross section is non-resonant. It is dominated by direct capture and by the tail of a ²¹Na state just below the proton threshold, the 2425 keV level, whose contribution has to be separated from direct capture in an R-matrix fit. The first resonance above threshold, at E_cm = 368 keV, is narrow and contributes at higher temperatures. The Notre Dame data of Lyons et al. (2018) between Eₚ = 0.5 and 2.0 MeV fixed the primary transitions to the bound states for the R-matrix extrapolation. The LUNA measurement of Masha et al. (2023) used a windowless neon gas target and two HPGe detectors deep underground to measure direct capture for the first time below E_cm = 352 keV, and remeasured the energy and strength of the 368 keV resonance.", "status": "improving", "statusNote": "Underground data now reach below E_cm = 352 keV and the 368 keV resonance strength is known to about 5%; the low-energy extrapolation still rests on the separation of direct capture from the subthreshold state.", "statusPlain": "Measured underground at low energies, and its main resonance is known to about 5%; the extension to the lowest energies still depends on a model.", "keywords": [], "methods": [ "direct-underground", "direct-surface" ], "measurements": [ { "year": 2018, "facility": "notre-dame", "lab": "", "method": "direct-surface", "energy": "Eₚ = 500–2000 keV", "note": "Cross sections for the primary transitions to the bound states of ²¹Na. An R-matrix fit separated direct capture from the subthreshold resonance; the resulting rate is lower than those in the libraries of the time by up to 20% in the temperature range of interest.", "refs": [ "lyons2018" ], "lowestKeV": null, "luna": false }, { "year": 2023, "facility": "luna-400", "lab": "", "method": "direct-underground", "energy": "E_cm below 352 keV, and the 368 keV resonance", "note": "First measurement of direct capture below E_cm = 352 keV, with a windowless gas target and two HPGe detectors. Resonance strength ωγ = 0.112 ± 0.002 (stat) ± 0.005 (sys) meV, three times more precise than before; the rate is 20% lower than previously adopted below 0.1 GK and unchanged above.", "refs": [ "masha2023" ], "lowestKeV": null, "luna": true }, { "year": 2025, "facility": "luna-400", "lab": "", "method": "direct-underground", "energy": "E_cm ≈ 368 keV resonance (366 keV in the report) and direct capture below 400 keV", "note": "Conference report on the LUNA campaign with a windowless gas target and two HPGe detectors, the campaign published in Masha et al. (2023); it describes the experiment and gives preliminary results on the resonance and on direct capture at the lowest energies.", "refs": [ "caciolli2025" ], "lowestKeV": null, "luna": true } ], "evaluations": [ "angulo1999" ], "rmatrix": [ "21Na" ], "openQuestions": [ "The contribution of the subthreshold 2425 keV state relative to direct capture at E_cm below 300 keV, which sets the rate at the lowest temperatures.", "The LUNA strength of the 368 keV resonance is three times more precise than earlier values and has not yet been checked by an independent measurement.", "A combined R-matrix analysis of the capture data at all energies, to fix the shape of the S-factor near the threshold." ], "facts": [], "related": [ "21Na-bp-21Ne", "21Ne-pg-22Na", "23Na-pa-20Ne", "19F-pg-20Ne" ], "q": { "value": 2.4318988640000003, "annihilation": false, "kinetic": 2.4318988640000003 }, "gamow": [ { "network": "nena", "label": "AGB hot-bottom burning", "T9": 0.08, "E0": 103.69596978767392, "width": 61.748685242029225 }, { "network": "nena", "label": "classical nova", "T9": 0.2, "E0": 191.00960948992628, "width": 132.50869866184786 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": 22.455, "stable": false, "text": "22.5 s" }, "references": [ "lyons2018", "masha2023", "caciolli2025", "angulo1999" ], "luna": true, "lunaYears": [ 2023, 2025 ] }, { "id": "21Na-bp-21Ne", "hasFile": true, "label": "²¹Na(β⁺ν)²¹Ne", "updated": null, "kind": "decay", "target": "21Na", "projectile": "", "ejectile": "e+ nu", "product": "21Ne", "from": { "code": "21Na", "A": 21, "Z": 11, "N": 10 }, "to": { "code": "21Ne", "A": 21, "Z": 10, "N": 11 }, "networks": [ "nena" ], "families": [ "nena" ], "importance": "minor", "summary": "²¹Na, made when ²⁰Ne captures a proton, turns into stable ²¹Ne by emitting a positron and a neutrino; the cycle then continues with a proton capture on ²¹Ne.", "role": "", "details": "", "status": null, "statusNote": "", "statusPlain": "", "keywords": [], "methods": [], "measurements": [], "evaluations": [], "rmatrix": [], "openQuestions": [], "facts": [], "related": [], "q": { "value": 3.5469199999999996, "annihilation": true, "kinetic": 2.5249220999999995 }, "gamow": [], "thermal": [], "windowNote": null, "halfLife": { "seconds": 22.455, "stable": false, "text": "22.5 s" }, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [], "luna": false, "lunaYears": [] }, { "id": "21Ne-pg-22Na", "hasFile": true, "label": "²¹Ne(p,γ)²²Na", "updated": null, "kind": "capture", "target": "21Ne", "projectile": "1H", "ejectile": "g", "product": "22Na", "from": { "code": "21Ne", "A": 21, "Z": 10, "N": 11 }, "to": { "code": "22Na", "A": 22, "Z": 11, "N": 11 }, "networks": [ "nena" ], "families": [ "nena" ], "importance": "major", "summary": "A proton capture on the rare neon isotope ²¹Ne that makes radioactive ²²Na. It is the second proton capture of the NeNa cycle.", "role": "²¹Ne is the rarest of the stable neon isotopes, and in hydrogen burning it is destroyed quickly by this reaction. Its rate therefore sets how much ²¹Ne survives in stars and how much ²²Na is made. In nova explosions, ²²Na is of special interest because its decay gives a γ-ray line that space telescopes search for; the amount predicted depends in part on this reaction.", "details": "The rate at the temperatures of hydrogen shell burning and of novae is given by a few narrow resonances. The LUNA measurement of Sidhu et al. (2025) remeasured the resonances at Eₚ = 127.3, 271.4, 272.3, 291.5 and 352.6 keV deep underground. The strengths of the 127.3, 271.4 and 291.5 keV resonances agree with earlier values within 1σ, while those of the 272.3 and 352.6 keV resonances, ωγ = 129.9 ± 5.8 meV and 14.9 ± 0.8 meV, are more than a factor 1.5 above the literature values. New branching ratios were obtained for the 127.3, 272.3 and 352.6 keV resonances, and the thermonuclear rate was updated for nova temperatures.", "status": "improving", "statusNote": "The main low-energy resonances were remeasured underground in 2025; two of them came out more than 50% stronger than in the earlier literature, with uncertainties of about 5%.", "statusPlain": "", "keywords": [], "methods": [ "direct-underground", "direct-surface" ], "measurements": [ { "year": 2025, "facility": "luna-400", "lab": "", "method": "direct-underground", "energy": "Eₚ = 127.3–352.6 keV (five resonances)", "note": "Resonance strengths measured deep underground. The 272.3 and 352.6 keV resonances are more than 1.5 times stronger than the literature values; new γ-ray branching ratios for three resonances and an updated rate for nova conditions.", "refs": [ "sidhu2025" ], "lowestKeV": null, "luna": true } ], "evaluations": [ "angulo1999" ], "rmatrix": [], "openQuestions": [ "The origin of the discrepancy between the new and the earlier strengths of the 272.3 and 352.6 keV resonances.", "An independent measurement of the 272.3 and 352.6 keV strengths with a different target and detection technique." ], "facts": [], "related": [ "21Na-bp-21Ne", "22Na-bp-22Ne", "20Ne-pg-21Na", "22Ne-pg-23Na" ], "q": { "value": 6.738581064000001, "annihilation": false, "kinetic": 6.738581064000001 }, "gamow": [ { "network": "nena", "label": "AGB hot-bottom burning", "T9": 0.08, "E0": 103.7752167877628, "width": 61.77227566467675 }, { "network": "nena", "label": "classical nova", "T9": 0.2, "E0": 191.15558371217642, "width": 132.55932218838376 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": 82107965.75940001, "stable": false, "text": "2.6 yr" }, "references": [ "sidhu2025", "angulo1999" ], "luna": true, "lunaYears": [ 2025 ] }, { "id": "22Na-bp-22Ne", "hasFile": true, "label": "²²Na(β⁺ν)²²Ne", "updated": null, "kind": "decay", "target": "22Na", "projectile": "", "ejectile": "e+ nu", "product": "22Ne", "from": { "code": "22Na", "A": 22, "Z": 11, "N": 11 }, "to": { "code": "22Ne", "A": 22, "Z": 10, "N": 12 }, "networks": [ "nena" ], "families": [ "nena" ], "importance": "minor", "summary": "²²Na turns into stable ²²Ne by emitting a positron and a neutrino, and the ²²Ne it leaves behind emits a γ-ray of 1275 keV; ²²Na made in nova explosions is a long-sought source of this γ-ray line.", "role": "", "details": "", "status": null, "statusNote": "", "statusPlain": "", "keywords": [], "methods": [], "measurements": [], "evaluations": [], "rmatrix": [], "openQuestions": [], "facts": [], "related": [], "q": { "value": 2.8433259999999994, "annihilation": true, "kinetic": 1.8213280999999995 }, "gamow": [], "thermal": [], "windowNote": null, "halfLife": { "seconds": 82107965.75940001, "stable": false, "text": "2.6 yr" }, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [], "luna": false, "lunaYears": [] }, { "id": "22Ne-pg-23Na", "hasFile": true, "label": "²²Ne(p,γ)²³Na", "updated": null, "kind": "capture", "target": "22Ne", "projectile": "1H", "ejectile": "g", "product": "23Na", "from": { "code": "22Ne", "A": 22, "Z": 10, "N": 12 }, "to": { "code": "23Na", "A": 23, "Z": 11, "N": 12 }, "networks": [ "nena" ], "families": [ "nena" ], "importance": "key", "summary": "The proton capture on ²²Ne that makes sodium. It is the main way stars produce ²³Na, the only stable sodium isotope, during hydrogen burning.", "role": "Many old star clusters in the Milky Way contain stars with more sodium and less oxygen than their neighbours. This pattern, called the sodium–oxygen anticorrelation, is thought to come from material that was burned at high temperature in an earlier generation of stars. Which stars did the burning, for example massive stars on the asymptotic giant branch (AGB stars), is still debated, and the answer depends on how fast ²²Ne turns into sodium. The same reaction sets part of the sodium and neon yields of nova explosions. For decades its rate was uncertain by large factors because several possible low-energy resonances had never been seen; most of them have now been measured or excluded.", "details": "At the temperatures of hot-bottom burning and of novae the rate is a sum of narrow resonances and of a non-resonant component, made of direct capture and of the tails of subthreshold states. Before 2014 several resonances below Eₚ = 300 keV were known only as upper limits or from indirect data, and the tentative resonances at Eₚ = 71 and 105 keV, together with the non-resonant component, left the rate at 0.1 GK uncertain by orders of magnitude.\nLUNA observed the Eₚ = 186 keV resonance in a feasibility study (Cavanna et al. 2014) and then measured the resonances at Eₚ = 156.2, 189.5 and 259.7 keV directly for the first time with a windowless ²²Ne gas target and two HPGe detectors (Cavanna et al. 2015; Depalo et al. 2016). The original strengths were later raised by 18–19% because the energy straggling of the beam had been neglected (erratum, 2018). A second LUNA campaign set upper limits of 6 × 10⁻¹¹ eV and 7 × 10⁻¹¹ eV on the 71 and 105 keV resonances and measured the off-resonance S-factor (Ferraro et al. 2018); a further analysis of direct capture and resonances at low energy followed (Takács et al. 2024). At TUNL, Kelly et al. (2017) measured the low-energy resonances with implanted targets. At higher energies, the resonances used to normalize the low-energy data were remeasured at HZDR (Depalo et al. 2015) and, in inverse kinematics, at DRAGON (Lennarz et al. 2020; Williams et al. 2020), where the strength of the E_cm = 458 keV reference resonance came out 0.439(22) eV, measured for the first time independently of other resonance strengths: lower than the two most recent forward-kinematics values, in agreement with three older ones.", "status": "improving", "statusNote": "The low-energy resonances are now measured or excluded and the rate uncertainty at 0.1 GK fell by about three orders of magnitude; the normalization to the higher-energy reference resonances and the non-resonant component remain under discussion.", "statusPlain": "Underground measurements have found or ruled out the low-energy resonances, and the uncertainty of the rate fell about a thousandfold; some details of the analysis are still debated.", "keywords": [], "methods": [ "direct-underground", "direct-surface", "inverse-kinematics" ], "measurements": [ { "year": 2014, "facility": "luna-400", "lab": "", "method": "direct-underground", "energy": "Eₚ = 186 keV resonance", "note": "Feasibility study for the underground campaign, including the beam-induced background. First direct observation of the 186 keV resonance, with a lower limit ωγ > 0.12 × 10⁻⁶ eV on its strength.", "refs": [ "cavanna2014" ], "lowestKeV": null, "luna": true }, { "year": 2015, "facility": "hzdr", "lab": "", "method": "direct-surface", "energy": "Eₚ = 436–1279 keV (five resonances)", "note": "Strengths of the 436, 639 and 661 keV resonances relative to those at 479 and 1279 keV, with a ²²Ne-implanted tantalum target. Consistent with but more precise than the literature, except the 661 keV resonance, which is ten times weaker; improved γ-ray branching ratios.", "refs": [ "depalo2015" ], "lowestKeV": null, "luna": false }, { "year": 2015, "facility": "luna-400", "lab": "", "method": "direct-underground", "energy": "Eₚ = 156.2, 189.5 and 259.7 keV", "note": "First direct observation of the three resonances, with strengths known to 2–7%, and much lower upper limits on three tentative resonances; the full account is in Depalo et al. (2016). An erratum raised the strengths by 18–19% after including the beam energy straggling, with unchanged astrophysical conclusions.", "refs": [ "cavanna2015", "depalo2016", "cavanna2018" ], "lowestKeV": null, "luna": true }, { "year": 2017, "facility": "tunl-lena", "lab": "", "method": "direct-surface", "energy": "Eₚ below 200 keV (ECR ion source) and higher energies (1 MV accelerator)", "note": "Independent measurement of the low-energy resonances with ²²Ne implanted in tantalum backings.", "refs": [ "kelly2017" ], "lowestKeV": null, "luna": false }, { "year": 2018, "facility": "luna-400", "lab": "", "method": "direct-underground", "energy": "Eₚ = 71 and 105 keV, and off-resonance", "note": "Upper limits of 6 × 10⁻¹¹ and 7 × 10⁻¹¹ eV (90% CL) on the two suggested resonances, and the off-resonance S-factor at very low energy, which constrains direct capture and a subthreshold resonance. The rate uncertainty at 0.1 GK was reduced by three orders of magnitude.", "refs": [ "ferraro2018" ], "lowestKeV": null, "luna": true }, { "year": 2020, "facility": "dragon", "lab": "", "method": "inverse-kinematics", "energy": "E_cm = 149–1222 keV (resonances); 282–511 keV (non-resonant)", "note": "First measurement in inverse kinematics, a ²²Ne beam on a windowless H₂ target, with different systematic uncertainties from all earlier work. The 458 keV reference resonance has ωγ = 0.439(22) eV, below the two most recent forward-kinematics values and in agreement with older ones; the rate is a factor of 4 above STARLIB-2013, with little effect on ²³Na in AGB stars but an effect on Ne–Al nuclei in novae.", "refs": [ "lennarz2020", "williams2020" ], "lowestKeV": null, "luna": false }, { "year": 2024, "facility": "luna-400", "lab": "", "method": "direct-underground", "energy": "direct capture down to Eₚ = 188 keV", "note": "Full account of the high-statistics LUNA data: new γ-decay branchings for the resonances at Eₚ = 156.2 and 259.7 keV, and partial cross sections for direct capture to several states of ²³Na down to Eₚ = 188 keV, the lowest energy so far. A new R-matrix fit gives a revised rate; tensions remain on some branching ratios and on the capture to excited states.", "refs": [ "takacs2024" ], "lowestKeV": null, "luna": true } ], "evaluations": [ "angulo1999" ], "rmatrix": [ "23Na" ], "openQuestions": [ "The strength of the E_cm = 458 keV reference resonance, where the DRAGON value, 0.439(22) eV, is lower than the two most recent forward-kinematics results; strengths normalized to it inherit the discrepancy.", "The size of the non-resonant component (direct capture and subthreshold states) between the resonances.", "Whether the updated rate is enough for AGB models to reproduce the sodium–oxygen anticorrelation in globular clusters." ], "facts": [], "related": [ "23Na-pg-24Mg", "23Na-pa-20Ne", "21Ne-pg-22Na", "22Ne-an-25Mg", "22Ne-ag-26Mg" ], "q": { "value": 8.794108564, "annihilation": false, "kinetic": 8.794108564 }, "gamow": [ { "network": "nena", "label": "AGB hot-bottom burning", "T9": 0.08, "E0": 103.84719168488733, "width": 61.79369350741318 }, { "network": "nena", "label": "classical nova", "T9": 0.2, "E0": 191.2881626062355, "width": 132.60528349845902 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "cavanna2014", "depalo2015", "cavanna2015", "depalo2016", "cavanna2018", "kelly2017", "ferraro2018", "lennarz2020", "williams2020", "takacs2024", "angulo1999" ], "luna": true, "lunaYears": [ 2014, 2015, 2018, 2024 ] }, { "id": "23Na-pa-20Ne", "hasFile": true, "label": "²³Na(p,α)²⁰Ne", "updated": null, "kind": "transfer", "target": "23Na", "projectile": "1H", "ejectile": "4He", "product": "20Ne", "from": { "code": "23Na", "A": 23, "Z": 11, "N": 12 }, "to": { "code": "20Ne", "A": 20, "Z": 10, "N": 10 }, "networks": [ "nena", "carbon-burning" ], "families": [ "nena", "carbon" ], "importance": "key", "summary": "The reaction that closes the NeNa cycle. A proton hits ²³Na and an alpha particle comes out, leaving ²⁰Ne, the nucleus the cycle started from.", "role": "Sodium made by hydrogen burning can be destroyed in two ways. In this reaction it goes back to neon and the cycle starts again; in the competing reaction, ²³Na(p,γ)²⁴Mg, it moves on to magnesium. The ratio of the two rates decides whether the NeNa cycle is closed or leaks into the MgAl cycle, and together they set how much sodium the hottest hydrogen-burning stars return to their surroundings. This is part of the puzzle of the sodium-rich stars in globular clusters.", "details": "At the temperatures of hot-bottom burning the rate depends on a few narrow low-energy resonances and on the alpha-particle branching of the states of ²⁴Mg that they populate. The lowest of them, at E_cm ≈ 133 keV (Eₚ = 140 keV in the (p,γ) channel), has not been observed directly in the (p,α) channel. Cesaratto et al. (2013) combined their upper limit on the (p,γ) strength with the α-particle branching ratio to set an upper limit of 0.88 × 10⁻⁹ eV on the (p,α) strength, which makes this resonance negligible for the rate, as summarized in Solar Fusion III (Acharya et al. 2025). The state was first identified with the ²³Na(³He,d)²⁴Mg reaction by Hale et al. (2004). The proton widths of the near-threshold states, which enter both the (p,α) and the (p,γ) channels, were remeasured with the ²³Na(³He,d)²⁴Mg reaction at TUNL (Marshall et al. 2023). The LUNA measurement of the (p,γ) channel (Boeltzig et al. 2019) observed the 140 keV resonance, whose strength in turn constrains the proton width of the state. A dedicated LUNA campaign on the (p,α) channel with an array of silicon detectors was announced (Ananna et al. 2024); no result has been published yet.", "status": "uncertain", "statusNote": "The rate at the lowest temperatures rests on resonances that have not been seen directly in the (p,α) channel, so it is set by upper limits and by the proton widths taken from the (p,γ) channel and from transfer reactions.", "statusPlain": "At the lowest temperatures the rate depends on resonances not yet seen in this reaction, so it rests on upper limits and on information from other reactions.", "keywords": [], "methods": [ "direct-surface", "direct-underground", "anc" ], "measurements": [ { "year": 2004, "facility": null, "lab": "", "method": "anc", "energy": "²³Na(³He,d)²⁴Mg at E(³He) = 20 MeV, θlab = 5°–35°", "note": "Proton-transfer spectroscopy of the states of ²⁴Mg near the proton threshold; a state corresponding to a previously unobserved resonance at E_cm = 138 keV may contribute to both the (p,γ) and (p,α) rates at low temperatures.", "refs": [ "hale2004" ], "lowestKeV": null, "luna": false }, { "year": 2013, "facility": "tunl-lena", "lab": "", "method": "direct-surface", "energy": "E_cm = 138 keV resonance", "note": "The upper limit on the (p,γ) strength of this resonance, combined with its α-particle branching ratio, gives an upper limit of 0.88 × 10⁻⁹ eV on the (p,α) strength.", "refs": [ "cesaratto2013", "acharya2025" ], "lowestKeV": null, "luna": false }, { "year": 2023, "facility": null, "lab": "TUNL, Durham", "method": "anc", "energy": "states of ²⁴Mg near the proton threshold", "note": "²³Na(³He,d)²⁴Mg proton transfer: new proton widths for the near-threshold states, in tension with the strength of the 133 keV resonance measured at LUNA in the (p,γ) channel. The energy of this state comes out about 9 keV below the value of Hale et al. (2004).", "refs": [ "marshall2023" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "angulo1999", "iliadis2010", "acharya2025" ], "rmatrix": [], "openQuestions": [ "A direct observation of the 133 keV resonance in the (p,α) channel, the aim of the planned LUNA campaign.", "The proton width of the 133 keV state, where transfer data and the direct (p,γ) strength disagree.", "The ratio of the (p,α) and (p,γ) rates near 0.05–0.1 GK, which decides whether material cycles back to neon or leaks to magnesium." ], "facts": [], "related": [ "23Na-pg-24Mg", "20Ne-pg-21Na", "22Ne-pg-23Na", "12C-12Cp-23Na" ], "q": { "value": 2.376133894, "annihilation": false, "kinetic": 2.376133894 }, "gamow": [ { "network": "nena", "label": "AGB hot-bottom burning", "T9": 0.08, "E0": 110.73008356083861, "width": 63.808654949255335 }, { "network": "nena", "label": "classical nova", "T9": 0.2, "E0": 203.96655784260574, "width": 136.92926088301022 }, { "network": "carbon-burning", "label": "core carbon burning, 15 M☉ star", "T9": 0.83, "E0": 526.7336104669504, "width": 448.26656222036945 }, { "network": "carbon-burning", "label": "superburst ignition, accreting neutron star", "T9": 0.5, "E0": 375.7096118807079, "width": 293.84136839866557 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "hale2004", "cesaratto2013", "acharya2025", "marshall2023", "angulo1999", "iliadis2010" ], "luna": false, "lunaYears": [] }, { "id": "23Na-pg-24Mg", "hasFile": true, "label": "²³Na(p,γ)²⁴Mg", "updated": null, "kind": "capture", "target": "23Na", "projectile": "1H", "ejectile": "g", "product": "24Mg", "from": { "code": "23Na", "A": 23, "Z": 11, "N": 12 }, "to": { "code": "24Mg", "A": 24, "Z": 12, "N": 12 }, "networks": [ "nena", "carbon-burning" ], "families": [ "nena", "carbon" ], "importance": "key", "summary": "A proton capture that destroys sodium and makes magnesium. It competes with ²³Na(p,α)²⁰Ne, which also destroys sodium but returns the material to neon.", "role": "When ²³Na captures a proton, the new nucleus either emits an alpha particle and goes back to ²⁰Ne, closing the NeNa cycle, or emits a γ-ray and becomes ²⁴Mg, leaking material into the MgAl cycle. This reaction is the leak. Together with its competitor it decides how much sodium survives hydrogen burning, which matters for the sodium-rich and oxygen-poor stars observed in old star clusters, and how much material flows on from neon to magnesium and aluminium.", "details": "At 50–110 MK the rate is dominated by narrow resonances at Eₚ = 140 and 251 keV and, at the low end of that range, by direct capture. The 140 keV resonance is quoted as E_cm = 138 keV or 133 keV in different works. A direct search at LENA gave only an upper limit on its strength (Cesaratto et al. 2013). The LUNA measurement of Boeltzig et al. (2019) observed it directly for the first time with a 4π BGO summing detector, ωγ = 1.46 (+0.58/−0.53) neV, and measured the 251 keV resonance with an HPGe detector, ωγ = 482(82) μeV. Direct capture, which had received little attention, was studied off resonance at Eₚ = 0.5–1.05 MeV by Boeltzig et al. (2022). A new ²³Na(³He,d) measurement at TUNL (Marshall et al. 2023) gives a proton width for the 133 keV resonance in clear tension with the LUNA strength.", "status": "improving", "statusNote": "The two key resonances were measured directly at LUNA, which limits the rate uncertainty at 0.07 GK to −35%/+50%; the strength of the lowest resonance is still in tension between direct and transfer data.", "statusPlain": "Its two key resonances were measured at LUNA, which narrows the rate to between about a third lower and a half higher than its best value; direct and indirect data still disagree on the lowest resonance.", "keywords": [], "methods": [ "direct-underground", "direct-surface", "anc" ], "measurements": [ { "year": 2013, "facility": "tunl-lena", "lab": "", "method": "direct-surface", "energy": "E_cm = 138 keV resonance", "note": "Search for the 138 keV resonance with the 200 kV accelerator and its ECR ion source; only an upper limit on the strength could be set, 5.17 neV at 95% confidence.", "refs": [ "cesaratto2013" ], "lowestKeV": null, "luna": false }, { "year": 2019, "facility": "luna-400", "lab": "", "method": "direct-underground", "energy": "Eₚ = 140 and 251 keV resonances", "note": "First direct observation of the 140 keV resonance (4π BGO), ωγ = 1.46 (+0.58/−0.53) neV, and the 251 keV resonance (HPGe), ωγ = 482(82) μeV. The rate uncertainty at 0.07 GK is reduced to at most −35%/+50%.", "refs": [ "boeltzig2019" ], "lowestKeV": 133, "luna": true }, { "year": 2022, "facility": "notre-dame", "lab": "", "method": "direct-surface", "energy": "Eₚ = 0.5–1.05 MeV", "note": "Off-resonance cross section, to determine the direct capture component that extrapolates to low energies.", "refs": [ "boeltzig2022" ], "lowestKeV": null, "luna": false }, { "year": 2023, "facility": null, "lab": "TUNL, Durham", "method": "anc", "energy": "states of ²⁴Mg near the proton threshold", "note": "²³Na(³He,d)²⁴Mg proton transfer to constrain the proton widths of the low-energy resonances; the width of the 133 keV resonance is in strong disagreement with the LUNA strength.", "refs": [ "marshall2023" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "angulo1999", "acharya2025" ], "rmatrix": [ "24Mg" ], "openQuestions": [ "The strength of the lowest resonance (E_cm ≈ 133 keV), where the direct LUNA value and the transfer data of Marshall et al. (2023) disagree.", "The direct capture S-factor at the energies of the Gamow window, which so far comes from extrapolation." ], "facts": [], "related": [ "23Na-pa-20Ne", "22Ne-pg-23Na", "24Mg-pg-25Al", "12C-12Cp-23Na" ], "q": { "value": 11.692695564000001, "annihilation": false, "kinetic": 11.692695564000001 }, "gamow": [ { "network": "nena", "label": "AGB hot-bottom burning", "T9": 0.08, "E0": 110.73008356083861, "width": 63.808654949255335 }, { "network": "nena", "label": "classical nova", "T9": 0.2, "E0": 203.96655784260574, "width": 136.92926088301022 }, { "network": "carbon-burning", "label": "core carbon burning, 15 M☉ star", "T9": 0.83, "E0": 526.7336104669504, "width": 448.26656222036945 }, { "network": "carbon-burning", "label": "superburst ignition, accreting neutron star", "T9": 0.5, "E0": 375.7096118807079, "width": 293.84136839866557 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "cesaratto2013", "boeltzig2019", "boeltzig2022", "marshall2023", "angulo1999", "acharya2025" ], "luna": true, "lunaYears": [ 2019 ] }, { "id": "24Mg-pg-25Al", "hasFile": true, "label": "²⁴Mg(p,γ)²⁵Al", "updated": null, "kind": "capture", "target": "24Mg", "projectile": "1H", "ejectile": "g", "product": "25Al", "from": { "code": "24Mg", "A": 24, "Z": 12, "N": 12 }, "to": { "code": "25Al", "A": 25, "Z": 13, "N": 12 }, "networks": [ "mgal" ], "families": [ "mgal" ], "importance": "major", "summary": "The first step of the MgAl cycle. ²⁴Mg, the most abundant magnesium isotope, captures a proton and becomes ²⁵Al, which quickly decays to ²⁵Mg.", "role": "This is one of the slowest proton captures in the MgAl cycle, so it controls how fast the most common magnesium isotope is converted into ²⁵Mg and, after one more capture, into radioactive ²⁶Al and stable ²⁷Al. In the hottest hydrogen-burning stars it destroys ²⁴Mg; some stars in globular clusters show less magnesium and more aluminium than their neighbours, a pattern attributed to this kind of burning.", "details": "The rate at the temperatures of hot-bottom burning is determined by direct capture and by the narrow resonance at E_cm = 214 keV. Limata et al. (2010) measured its strength at LUNA, together with resonances in ²⁵Mg + p and ²⁶Mg + p, with a precision higher than previously achieved; these resonances also serve as normalization references for weaker, lower-energy resonances in the magnesium isotopes, where absolute measurements suffer from beam-induced background and changing target stoichiometry.", "status": "well-known", "statusNote": "The resonance that dominates at hydrogen-burning temperatures has been measured directly underground with good precision; below it the rate relies on extrapolated direct capture.", "statusPlain": "The resonance that matters most in hydrogen-burning stars has been measured underground with good precision; at lower energies the rate still relies on an extrapolation.", "keywords": [], "methods": [ "direct-underground", "direct-surface" ], "measurements": [ { "year": 2010, "facility": "luna-400", "lab": "", "method": "direct-underground", "energy": "E_cm = 214 keV resonance", "note": "Resonance strength measured underground with several techniques, more precise than earlier values; also intended as a reference for lower-energy resonances.", "refs": [ "limata2010" ], "lowestKeV": null, "luna": true } ], "evaluations": [ "angulo1999" ], "rmatrix": [], "openQuestions": [ "The direct capture S-factor below the 214 keV resonance, which so far comes from extrapolation of higher-energy data." ], "facts": [], "related": [ "25Al-bp-25Mg", "25Mg-pg-26Al", "23Na-pg-24Mg", "27Al-pa-24Mg" ], "q": { "value": 2.271363063999999, "annihilation": false, "kinetic": 2.271363063999999 }, "gamow": [ { "network": "mgal", "label": "AGB hot-bottom burning", "T9": 0.08, "E0": 117.4114634246133, "width": 65.70554573406872 }, { "network": "mgal", "label": "classical nova", "T9": 0.2, "E0": 216.27376477886952, "width": 140.99986624754663 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": 7.1666, "stable": false, "text": "7.17 s" }, "references": [ "limata2010", "angulo1999" ], "luna": true, "lunaYears": [ 2010 ] }, { "id": "25Al-bp-25Mg", "hasFile": true, "label": "²⁵Al(β⁺ν)²⁵Mg", "updated": null, "kind": "decay", "target": "25Al", "projectile": "", "ejectile": "e+ nu", "product": "25Mg", "from": { "code": "25Al", "A": 25, "Z": 13, "N": 12 }, "to": { "code": "25Mg", "A": 25, "Z": 12, "N": 13 }, "networks": [ "mgal" ], "families": [ "mgal" ], "importance": "minor", "summary": "²⁵Al, made when ²⁴Mg captures a proton, turns into stable ²⁵Mg by emitting a positron and a neutrino; ²⁵Mg is the nucleus from which radioactive ²⁶Al is made.", "role": "", "details": "", "status": null, "statusNote": "", "statusPlain": "", "keywords": [], "methods": [], "measurements": [], "evaluations": [], "rmatrix": [], "openQuestions": [], "facts": [], "related": [], "q": { "value": 4.276810000000001, "annihilation": true, "kinetic": 3.2548121000000014 }, "gamow": [], "thermal": [], "windowNote": null, "halfLife": { "seconds": 7.1666, "stable": false, "text": "7.17 s" }, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [], "luna": false, "lunaYears": [] }, { "id": "25Mg-pg-26Al", "hasFile": true, "label": "²⁵Mg(p,γ)²⁶Al", "updated": null, "kind": "capture", "target": "25Mg", "projectile": "1H", "ejectile": "g", "product": "26Al", "from": { "code": "25Mg", "A": 25, "Z": 12, "N": 13 }, "to": { "code": "26Al", "A": 26, "Z": 13, "N": 13 }, "networks": [ "mgal" ], "families": [ "mgal" ], "importance": "key", "summary": "The reaction that makes radioactive ²⁶Al in hydrogen-burning stars. The decay of ²⁶Al gives the 1809 keV γ-ray line seen across the Milky Way.", "role": "²⁶Al lives long enough to spread through the Galaxy but not so long that it piles up, so the 1809 keV γ-ray line from its decay shows where nuclei were made in the last few million years. Space telescopes map this line, and the amount of ²⁶Al they see is compared with the predicted output of massive stars, Wolf–Rayet stars, AGB stars and novae. Most of that ²⁶Al is made by this reaction. The reaction can leave ²⁶Al in its ground state, which gives the γ-ray line, or in a short-lived excited state, the isomer ²⁶ᵐAl, which decays straight to ²⁶Mg without it. How the captures divide between the two decides how much of the line a star contributes. The same reaction also matters for the ²⁶Al once present in the early Solar System, recorded in meteorites, and for the magnesium and aluminium abundances of globular-cluster stars.", "details": "Between 50 and 150 MK the rate is given by a handful of narrow resonances, of which the one at E_cm = 92 keV dominates around 100 MK. Each resonance decays by a γ-ray cascade that ends either in the ground state or in the isomer of ²⁶Al, so the rate has to be split using the measured ground-state fraction of each resonance. At LUNA, Limata et al. (2010) measured the strength of the 304 keV resonance as a reference for the weaker ones, and Strieder et al. (2012) observed the 92 keV resonance directly for the first time with a 4π BGO summing detector, ωγ = (2.9 ± 0.6) × 10⁻¹⁰ eV, and studied the γ-ray branchings and strength of the 189 keV resonance with an HPGe detector, finding a strength 20% larger than earlier works. The rate derived from these data (Straniero et al. 2013) increases the production of the isomer by up to a factor of 5 between 50 and 150 MK and doubles the total rate at 100 MK, so less ²⁶Al is made in the ground state. The JUNA collaboration chose the 92 keV resonance for the first experiment at the China Jinping Underground Laboratory and reported a precise measurement of its strength (Su et al. 2022). The γ-ray decay schemes of the low-energy resonances were first studied by Iliadis et al. (1990). For the 92 keV resonance, Kankainen et al. (2021) identified four γ-ray transitions and obtained a ground-state fraction f₀ = 0.52(2)(6), the most precise value so far and at the low end of those adopted before, which lowers the production of ²⁶Al in its ground state.", "status": "improving", "statusNote": "The key low-energy resonances were measured directly underground, at LUNA and at JUNA; the split between ground state and isomer, especially for the 92 keV resonance, is the largest remaining uncertainty for the ²⁶Al ground-state yield.", "statusPlain": "The key resonances were measured directly underground, at LUNA and at JUNA. The main uncertainty left is how much of the product is made in the long-lived form of aluminium-26, the one that γ-ray telescopes see in the Galaxy.", "keywords": [], "methods": [ "direct-underground", "direct-surface" ], "measurements": [ { "year": 1990, "facility": null, "lab": "", "method": "direct-surface", "energy": "low-energy (p,γ) resonances", "note": "γ-ray decay schemes of the low-energy resonances, measured together with resonances in ²⁶Mg(p,γ) and ²⁷Al(p,γ).", "refs": [ "iliadis1990" ], "lowestKeV": null, "luna": false }, { "year": 2010, "facility": "luna-400", "lab": "", "method": "direct-underground", "energy": "E_cm = 304 keV resonance", "note": "Strength of the 304 keV resonance with higher accuracy than before, to serve as a normalization for the low-energy resonances.", "refs": [ "limata2010" ], "lowestKeV": null, "luna": true }, { "year": 2012, "facility": "luna-400", "lab": "", "method": "direct-underground", "energy": "E_cm = 92 and 189 keV resonances", "note": "First direct observation of the 92 keV resonance with a 4π BGO summing detector, ωγ = (2.9 ± 0.6) × 10⁻¹⁰ eV. γ-ray branchings and strength of the 189 keV resonance with an HPGe detector, 20% higher than previous values.", "refs": [ "strieder2012" ], "lowestKeV": null, "luna": true }, { "year": 2022, "facility": "juna", "lab": "", "method": "direct-underground", "energy": "E_cm = 92 keV resonance", "note": "First experiment at JUNA in the China Jinping Underground Laboratory: a precise measurement of the 92 keV resonance, independent of the LUNA one.", "refs": [ "su2022" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "straniero2013", "angulo1999" ], "rmatrix": [], "openQuestions": [ "The ground-state fraction of the 92 keV resonance, which sets how much of the rate produces ²⁶Al in its ground state and therefore the 1809 keV line.", "The comparison of the LUNA and JUNA strengths of the 92 keV resonance, the two direct measurements in deep underground laboratories.", "The effect of the higher isomer production on the ²⁶Al yields of Wolf–Rayet and massive AGB stars." ], "facts": [ { "text": "Only about half of the aluminium-26 made at the key 92 keV resonance will ever shine at 1809 keV; the rest is born in a short-lived excited state that decays without that γ-ray line.", "refs": [ "kankainen2021" ] }, { "text": "Making aluminium-26 is only half the story: in massive stars neutrons also destroy it. In 2021 CERN's n_TOF measured eleven ²⁶Al(n,p) resonances, nine of them for the first time; the strengths came out clearly lower than the only earlier values.", "refs": [ "ledererwoods2021" ] } ], "related": [ "26Al-bp-26Mg", "24Mg-pg-25Al", "25Al-bp-25Mg", "26Mg-pg-27Al", "22Ne-an-25Mg" ], "q": { "value": 6.306331064, "annihilation": false, "kinetic": 6.306331064 }, "gamow": [ { "network": "mgal", "label": "AGB hot-bottom burning", "T9": 0.08, "E0": 117.4747450518838, "width": 65.72325011159727 }, { "network": "mgal", "label": "classical nova", "T9": 0.2, "E0": 216.39033053294438, "width": 141.03785870062848 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": 22626315942000, "stable": false, "text": "717 000 yr" }, "references": [ "iliadis1990", "limata2010", "strieder2012", "su2022", "straniero2013", "angulo1999", "kankainen2021", "ledererwoods2021" ], "luna": true, "lunaYears": [ 2010, 2012 ] }, { "id": "26Al-bp-26Mg", "hasFile": true, "label": "²⁶Al(β⁺ν)²⁶Mg", "updated": null, "kind": "decay", "target": "26Al", "projectile": "", "ejectile": "e+ nu", "product": "26Mg", "from": { "code": "26Al", "A": 26, "Z": 13, "N": 13 }, "to": { "code": "26Mg", "A": 26, "Z": 12, "N": 14 }, "networks": [ "mgal" ], "families": [ "mgal" ], "importance": "minor", "summary": "²⁶Al in its ground state lives for about a million years. It decays to an excited state of ²⁶Mg, which at once emits a γ-ray of 1809 keV. Space telescopes see this γ-ray line across the Milky Way: a map of where nuclei were made in the last few million years. ²⁶Al also has a second, excited form, the isomer ²⁶ᵐAl. It decays within seconds, straight to the ground state of ²⁶Mg, and gives no 1809 keV γ-ray. Only ²⁶Al made in its ground state feeds the line.", "role": "", "details": "", "status": null, "statusNote": "", "statusPlain": "", "keywords": [], "methods": [], "measurements": [], "evaluations": [], "rmatrix": [], "openQuestions": [], "facts": [], "related": [], "q": { "value": 4.004403999999999, "annihilation": true, "kinetic": 2.9824060999999995 }, "gamow": [], "thermal": [], "windowNote": null, "halfLife": { "seconds": 22626315942000, "stable": false, "text": "717 000 yr" }, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [], "luna": false, "lunaYears": [] }, { "id": "26Mg-pg-27Al", "hasFile": true, "label": "²⁶Mg(p,γ)²⁷Al", "updated": null, "kind": "capture", "target": "26Mg", "projectile": "1H", "ejectile": "g", "product": "27Al", "from": { "code": "26Mg", "A": 26, "Z": 12, "N": 14 }, "to": { "code": "27Al", "A": 27, "Z": 13, "N": 14 }, "networks": [ "mgal" ], "families": [ "mgal" ], "importance": "major", "summary": "A proton capture on the heaviest stable magnesium isotope that makes ²⁷Al, the only stable isotope of aluminium.", "role": "²⁶Mg is made both by the decay of ²⁶Al and directly in earlier burning stages. This reaction turns it into ²⁷Al, so it feeds the aluminium seen in stars. In globular clusters some stars show more aluminium and less magnesium than others, and models of these stars need this rate together with the other proton captures of the MgAl cycle.", "details": "The rate at hydrogen-burning temperatures is given by narrow resonances. Limata et al. (2010) measured the strength of the E_cm = 326 keV resonance at LUNA with a precision higher than previously achieved, as a normalization reference for the weaker resonances at lower energies, whose absolute measurement is limited by beam-induced background and target stoichiometry.", "status": "uncertain", "statusNote": "The reference resonance is measured precisely; the weaker resonances below it, which matter at the lowest temperatures, are less well constrained.", "statusPlain": "", "keywords": [], "methods": [ "direct-underground", "direct-surface" ], "measurements": [ { "year": 1990, "facility": null, "lab": "", "method": "direct-surface", "energy": "low-energy (p,γ) resonances", "note": "γ-ray decay schemes of low-energy resonances, including a newly observed ²⁶Mg(p,γ)²⁷Al resonance; measured together with ²⁵Mg(p,γ) and ²⁷Al(p,γ).", "refs": [ "iliadis1990" ], "lowestKeV": null, "luna": false }, { "year": 2010, "facility": "luna-400", "lab": "", "method": "direct-underground", "energy": "E_cm = 326 keV resonance", "note": "Resonance strength measured underground, more precise than earlier values, for use as a normalization reference.", "refs": [ "limata2010" ], "lowestKeV": null, "luna": true } ], "evaluations": [ "angulo1999" ], "rmatrix": [], "openQuestions": [ "Direct measurements of the resonances below E_cm = 326 keV, which dominate the rate in hot-bottom burning." ], "facts": [], "related": [ "26Al-bp-26Mg", "25Mg-pg-26Al", "27Al-pg-28Si", "27Al-pa-24Mg", "22Ne-ag-26Mg" ], "q": { "value": 8.271287064000001, "annihilation": false, "kinetic": 8.271287064000001 }, "gamow": [ { "network": "mgal", "label": "AGB hot-bottom burning", "T9": 0.08, "E0": 117.53304635038505, "width": 65.73955691663247 }, { "network": "mgal", "label": "classical nova", "T9": 0.2, "E0": 216.4977224429895, "width": 141.0728520532169 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "iliadis1990", "limata2010", "angulo1999" ], "luna": true, "lunaYears": [ 2010 ] }, { "id": "27Al-pa-24Mg", "hasFile": true, "label": "²⁷Al(p,α)²⁴Mg", "updated": null, "kind": "transfer", "target": "27Al", "projectile": "1H", "ejectile": "4He", "product": "24Mg", "from": { "code": "27Al", "A": 27, "Z": 13, "N": 14 }, "to": { "code": "24Mg", "A": 24, "Z": 12, "N": 12 }, "networks": [ "mgal" ], "families": [ "mgal" ], "importance": "key", "summary": "The reaction that closes the MgAl cycle. A proton hits ²⁷Al and an alpha particle comes out, leaving ²⁴Mg, where the cycle started.", "role": "Aluminium made in hydrogen burning can either return to magnesium through this reaction or move on to silicon through ²⁷Al(p,γ)²⁸Si. The balance between the two sets how much aluminium survives, and whether material stays inside the MgAl cycle or leaks out of it. This matters for the aluminium-rich and magnesium-poor stars observed in globular clusters and for the aluminium made in nova explosions.", "details": "At the temperatures of hot-bottom burning and of novae the rate depends on narrow resonances close to the proton threshold and on the α-particle branching of the corresponding states of ²⁸Si. Many of these resonances are too weak to have been observed directly in the (p,α) channel, so the compiled rates (Angulo et al. 1999; Iliadis et al. 2010) combine upper limits, the (p,γ) strengths of the same resonances and proton widths from transfer reactions.\n\nThe Trojan Horse method gave the first data in this energy range. The three-body reaction ²H(²⁷Al,α²⁴Mg)n covered centre-of-mass energies up to 1.5 MeV and showed a group of resonances close to the Gamow window of stellar hydrogen burning, 70–120 keV (Palmerini et al. 2021). A second analysis determined the contribution of the 84.3 keV resonance, set upper limits on the nearby ones and gave a new recommended rate (La Cognata et al. 2022).", "status": "uncertain", "statusNote": "The low-energy resonances that set the rate are known only from the indirect Trojan Horse method and from upper limits; no direct measurement reaches the energies of hydrogen burning in stars.", "statusPlain": "", "keywords": [], "methods": [ "thm", "direct-surface", "anc" ], "measurements": [ { "year": 2021, "facility": null, "lab": "", "method": "thm", "energy": "²H(²⁷Al,α²⁴Mg)n, E up to 1.5 MeV", "note": "First Trojan Horse study of the reaction; a group of resonances appears close to the 70–120 keV Gamow window of hydrogen burning.", "refs": [ "palmerini2021" ], "lowestKeV": null, "luna": false }, { "year": 2022, "facility": null, "lab": "", "method": "thm", "energy": "E = 84.3 keV resonance and its neighbours", "note": "Contribution of the 84.3 keV resonance determined and upper limits set on the nearby resonances; new recommended reaction rate.", "refs": [ "lacognata2022" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "angulo1999", "iliadis2010" ], "rmatrix": [], "openQuestions": [ "Direct observation of the low-energy resonances in the (p,α) channel, which requires the low background of an underground laboratory.", "The ratio of the (p,α) and (p,γ) rates on ²⁷Al, which decides whether the MgAl cycle closes or leaks to silicon." ], "facts": [], "related": [ "27Al-pg-28Si", "24Mg-pg-25Al", "23Na-pa-20Ne" ], "q": { "value": 1.6007731939999998, "annihilation": false, "kinetic": 1.6007731939999998 }, "gamow": [ { "network": "mgal", "label": "AGB hot-bottom burning", "T9": 0.08, "E0": 124.03235778122558, "width": 67.53272526922579 }, { "network": "mgal", "label": "classical nova", "T9": 0.2, "E0": 228.46955645833452, "width": 144.92087576339662 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "palmerini2021", "lacognata2022", "angulo1999", "iliadis2010" ], "luna": false, "lunaYears": [] }, { "id": "27Al-pg-28Si", "hasFile": true, "label": "²⁷Al(p,γ)²⁸Si", "updated": null, "kind": "capture", "target": "27Al", "projectile": "1H", "ejectile": "g", "product": "28Si", "from": { "code": "27Al", "A": 27, "Z": 13, "N": 14 }, "to": { "code": "28Si", "A": 28, "Z": 14, "N": 14 }, "networks": [ "mgal" ], "families": [ "mgal" ], "importance": "key", "summary": "A proton capture that turns aluminium into silicon. It is the way out of the MgAl cycle, in competition with ²⁷Al(p,α)²⁴Mg, which keeps material inside it.", "role": "When ²⁷Al captures a proton, the new nucleus either emits an alpha particle and returns to magnesium, or emits a γ-ray and becomes ²⁸Si. This reaction is the second route. It sets how much aluminium the hottest hydrogen-burning stars destroy, how much silicon they make, and how much material escapes the MgAl cycle towards heavier elements in nova explosions.", "details": "At hydrogen-burning temperatures the rate is a sum of narrow resonances near the proton threshold and of direct capture. The weakest low-energy resonances are known only from upper limits or from transfer reactions, so the low- temperature rate depends on indirect data; at nova temperatures it is dominated by resonances that have been measured directly. Iliadis et al. (1990) measured the γ-ray decay schemes of low-energy resonances and gave new spin-parity and isospin assignments for states of ²⁸Si. Harissopulos et al. (2000) measured the strengths of 26 resonances between Eₚ = 200 and 1120 keV with two 4π NaI(Tl) summing detectors, and obtained the direct-capture cross section from yields at nine beam energies between 490 and 1150 keV.", "status": "uncertain", "statusNote": "At the lowest temperatures the rate depends on resonances that are too weak to have been observed directly; at nova temperatures it rests on measured resonances.", "statusPlain": "", "keywords": [], "methods": [ "direct-surface", "anc" ], "measurements": [ { "year": 1990, "facility": null, "lab": "", "method": "direct-surface", "energy": "low-energy (p,γ) resonances", "note": "γ-ray decay schemes of the low-energy resonances, with new spin-parity and isospin assignments for states of ²⁸Si; measured together with resonances in ²⁵Mg(p,γ) and ²⁶Mg(p,γ).", "refs": [ "iliadis1990" ], "lowestKeV": null, "luna": false }, { "year": 2000, "facility": null, "lab": "Ruhr-Universität Bochum, Bochum, and NCSR Demokritos, Athens", "method": "direct-surface", "energy": "Eₚ = 0.2–1.12 MeV", "note": "Strengths of 26 resonances with two 4π NaI(Tl) summing detectors, and the direct-capture cross section from yields at nine energies between 490 and 1150 keV, combined with earlier data on the non-resonant capture.", "refs": [ "harissopulos2000" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "angulo1999", "iliadis2010" ], "rmatrix": [], "openQuestions": [ "Direct measurements of the lowest-energy resonances, which require an underground laboratory.", "The competition with ²⁷Al(p,α)²⁴Mg, which decides whether the MgAl cycle closes." ], "facts": [], "related": [ "27Al-pa-24Mg", "26Mg-pg-27Al", "24Mg-pg-25Al" ], "q": { "value": 11.584908164, "annihilation": false, "kinetic": 11.584908164 }, "gamow": [ { "network": "mgal", "label": "AGB hot-bottom burning", "T9": 0.08, "E0": 124.03235778122558, "width": 67.53272526922579 }, { "network": "mgal", "label": "classical nova", "T9": 0.2, "E0": 228.46955645833452, "width": 144.92087576339662 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "iliadis1990", "harissopulos2000", "angulo1999", "iliadis2010" ], "luna": false, "lunaYears": [] }, { "id": "4He-aa-12C", "hasFile": true, "label": "⁴He(αα,γ)¹²C", "updated": null, "kind": "fusion", "target": "4He", "projectile": "2 4He", "ejectile": "g", "product": "12C", "from": { "code": "4He", "A": 4, "Z": 2, "N": 2 }, "to": { "code": "12C", "A": 12, "Z": 6, "N": 6 }, "networks": [ "he-burning" ], "families": [ "he" ], "importance": "key", "summary": "The triple-alpha process: three helium nuclei join to make carbon. Almost all the carbon in the Universe, including the carbon in living things, was made this way inside stars.", "role": "Two helium nuclei cannot stick together for long. They form beryllium-8, which falls apart again in a tiny fraction of a second. In the hot, dense core of a helium-burning star a third helium nucleus sometimes arrives before that happens. Carbon then forms, but only because carbon-12 has an excited state, the Hoyle state, at just the right energy to catch the three particles. In 1954 Fred Hoyle argued that such a state had to exist for stars to make as much carbon as we see, and experiments soon found it. The rate of this process sets how fast helium burns and, together with the next step, carbon-12 capturing a helium nucleus, decides how much carbon and how much oxygen a star leaves behind.", "details": "At helium-burning temperatures (T₉ ≈ 0.1–0.2) the rate proceeds sequentially: α + α forms the unbound ⁸Be ground state in equilibrium, and ⁸Be + α populates the 7.65 MeV 0⁺ Hoyle state of ¹²C (Salpeter 1952; Hoyle 1954). The Hoyle state decays almost always back to three α particles; the rate is therefore proportional to its radiative width Γ_rad = Γ_γ + Γ_π, the sum of the γ-decay and E0 pair-decay widths. Γ_rad is not measured directly but obtained as the product of three quantities: the γ-decay branching ratio Γ_rad/Γ, the pair-decay branching ratio Γ_π/Γ and the pair-decay width Γ_π (Freer and Fynbo 2014).\n\nRecent work has questioned the adopted Γ_rad/Γ. Kibédi et al. (2020) found Γ_rad/Γ = 6.2(6)×10⁻⁴ from p–γ–γ coincidences and, combined with the new pair-decay branching ratio of Eriksen et al. (2020), Γ_rad = 5.1(6)×10⁻³ eV, about 34% above the previously adopted value. Eriksen et al. alone had lowered Γ_rad by 11% through a 14% larger Γ_π/Γ. Rana et al. (2024) found Γ_rad/Γ = 4.01(30)×10⁻⁴ from p–γ–γ triple coincidences, consistent with the previously adopted value and not with the 34% increase. Dell'Aquila et al. (2024), with charged-particle coincidences, found Γ_rad/Γ = 4.4(6)×10⁻⁴. Paulsen et al. (2025) remeasured the γ-decay branching ratio at Oslo, Γ_γ/Γ = 4.0(3)×10⁻⁴ and Γ_rad/Γ = 4.1(4)×10⁻⁴, and reanalysed the 2014 data used by Kibédi et al.: after correcting several issues in that analysis they obtain 4.6(6)×10⁻⁴, no longer discrepant with the ENSDF average of 4.16(11)×10⁻⁴. The measurements have therefore converged on the value adopted before 2020, with Kibédi et al. (2020) the outlier, now reanalysed. At high temperatures (T₉ ≳ 1) broader states above the Hoyle state and non-resonant contributions matter: Fynbo et al. (2005) mapped the ¹²C continuum in β decay, and Tsumura et al. (2021) gave the first value for the radiative-decay probability of the 3⁻₁ state.", "status": "improving", "statusNote": "The rate depends on how often the Hoyle state of carbon-12 settles into stable carbon instead of breaking up again into three helium nuclei. That probability is tiny; a 2020 measurement put it about 30% higher, but the measurements of 2024–2025 and a reanalysis of the 2020 data agree on the earlier value, about 4.1 in 10 000.", "statusPlain": "", "keywords": [ "Hoyle state", "triple alpha", "3α", "carbon-12" ], "methods": [ "direct-surface", "inverse-kinematics", "theory" ], "measurements": [ { "year": 1953, "facility": "kellogg", "lab": "", "method": "direct-surface", "energy": "¹²C excitation 4.4–9.2 MeV via ¹⁴N(d,α)¹²C", "note": "Magnetic analysis of the α spectrum from ¹⁴N(d,α)¹²C found a level at 7.68 ± 0.03 MeV, the state Hoyle had predicted; the paper credits Hoyle with its astrophysical significance.", "refs": [ "dunbar1953" ], "lowestKeV": null, "luna": false }, { "year": 1957, "facility": "kellogg", "lab": "", "method": "direct-surface", "energy": "β decay of ¹²B", "note": "α particles following the β decay of ¹²B showed that the 7.65 MeV state breaks up into ⁸Be + α, so it can be formed from three α particles in a star; this fixed its energy and spin-parity.", "refs": [ "cook1957" ], "lowestKeV": null, "luna": false }, { "year": 2005, "facility": null, "lab": "ISOLDE, CERN, Geneva, and IGISOL, Jyväskylä", "method": "direct-surface", "energy": "¹²C continuum populated in the β decay of ¹²B and ¹²N", "note": "¹²B was produced at ISOLDE and ¹²N at IGISOL. Breakup spectra of the ¹²C states fed in their β decay showed a dominant resonance near 11 MeV and no evidence for a previously reported state at 9.1 MeV; the revised rate is higher below 5×10⁷ K and much lower above 10⁹ K.", "refs": [ "fynbo2005" ], "lowestKeV": null, "luna": false }, { "year": 2020, "facility": "anu", "lab": "", "method": "direct-surface", "energy": "E0 pair decay of the 7.65 MeV state, ¹²C(p,p′) at 10.5 MeV", "note": "e⁺e⁻ pairs detected with the Super-e spectrometer. New pair-decay branching ratio, 14% larger than the adopted Γ_π/Γ = 6.7(6)×10⁻⁶, with the uncertainty reduced from 9% to 5%; on its own it lowers Γ_rad and the rate by 11%.", "refs": [ "eriksen2020" ], "lowestKeV": null, "luna": false }, { "year": 2020, "facility": "oslo-ocl", "lab": "", "method": "direct-surface", "energy": "¹²C(p,p′) at 10.7 MeV", "note": "Proton–γ–γ triple coincidences gave Γ_rad/Γ = 6.2(6)×10⁻⁴ and Γ_rad = 5.1(6)×10⁻³ eV, 34% above the adopted value.", "refs": [ "kibedi2020" ], "lowestKeV": null, "luna": false }, { "year": 2021, "facility": "rcnp-osaka", "lab": "", "method": "inverse-kinematics", "energy": "¹H(¹²C,¹²C p), 3⁻₁ state at 9.64 MeV", "note": "First experimental radiative-decay probability of the 3⁻₁ state, 1.3 (+1.2/−1.1)×10⁻⁶; the state increases the triple-α rate at high temperature, where it had been assumed to be negligible.", "refs": [ "tsumura2021" ], "lowestKeV": null, "luna": false }, { "year": 2024, "facility": null, "lab": "Variable Energy Cyclotron Centre, Kolkata", "method": "direct-surface", "energy": "¹²C(p,p′γγ) triple coincidences, and a kinematically complete ¹²C(p,p′) measurement", "note": "Γ_rad/Γ = 4.01(30)×10⁻⁴, and 4.04(30)×10⁻⁴ from the independent kinematically complete experiment; with the adopted pair-decay values, Γ_rad = 3.75(40)×10⁻³ eV, consistent with the value adopted before 2020 and not with the 34% increase.", "refs": [ "rana2024" ], "lowestKeV": null, "luna": false }, { "year": 2024, "facility": null, "lab": "", "method": "direct-surface", "energy": "Hoyle state, charged-particle coincidences", "note": "An almost background-free measurement with charged-particle coincidences and a two-dimensional map of the coincidence efficiency: Γ_rad/Γ = 4.4(6)×10⁻⁴.", "refs": [ "dellaquila2024" ], "lowestKeV": null, "luna": false }, { "year": 2025, "facility": "oslo-ocl", "lab": "", "method": "direct-surface", "energy": "¹²C(p,p′) at 10.8 MeV", "note": "Remeasurement of the γ-decay branching ratio from triple coincidences, checked with a surrogate γ-ray cascade in ²⁸Si, together with a reanalysis of the 2014 data used by Kibédi et al.: Γ_γ/Γ = 4.0(3)×10⁻⁴ and Γ_rad/Γ = 4.1(4)×10⁻⁴; the corrected analysis of the 2014 data gives 4.6(6)×10⁻⁴, no longer in conflict with the ENSDF average.", "refs": [ "paulsen2025" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "angulo1999", "freer2014" ], "rmatrix": [ "8Be" ], "openQuestions": [ "The γ-decay branching ratio of the Hoyle state has converged (Rana 2024, Dell'Aquila 2024, Paulsen 2025 and the reanalysis of the 2020 data agree at about 4.1×10⁻⁴); Γ_rad still depends on the pair-decay quantities Γ_π/Γ and Γ_π that multiply it.", "The rate at T₉ ≳ 1, which depends on broad higher-lying states and on the 3⁻₁ radiative width, known only to about a factor of two." ], "facts": [ { "text": "Only about 4 in every 10 000 Hoyle states settle into carbon-12; the rest break up again into three helium nuclei. All the carbon in the Universe comes through that small fraction.", "refs": [ "paulsen2025", "rana2024" ] } ], "related": [ "12C-ag-16O" ], "q": { "value": 7.27474761, "annihilation": false, "kinetic": 7.27474761 }, "gamow": [], "thermal": [], "windowNote": "Three helium nuclei do not meet at once. Two of them form ⁸Be, which lives about 10⁻¹⁶ s; a third captures on it through the 7.65 MeV Hoyle state of ¹²C before it falls apart. The rate is set by the energies and widths of these two resonances, not by a Gamow window.", "halfLife": null, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "dunbar1953", "cook1957", "fynbo2005", "eriksen2020", "kibedi2020", "tsumura2021", "rana2024", "dellaquila2024", "paulsen2025", "angulo1999", "freer2014" ], "luna": false, "lunaYears": [] }, { "id": "12C-ag-16O", "hasFile": true, "label": "¹²C(α,γ)¹⁶O", "updated": null, "kind": "capture", "target": "12C", "projectile": "4He", "ejectile": "g", "product": "16O", "from": { "code": "12C", "A": 12, "Z": 6, "N": 6 }, "to": { "code": "16O", "A": 16, "Z": 8, "N": 8 }, "networks": [ "he-burning" ], "families": [ "he" ], "importance": "key", "summary": "Carbon-12 captures a helium nucleus and becomes oxygen-16. Together with the triple-alpha process, it decides how much carbon and how much oxygen stars make.", "role": "While helium burns in the core of a star, carbon is made by the triple-alpha process and destroyed by this reaction. When the helium runs out, the balance between the two leaves a definite ratio of carbon to oxygen. That ratio shapes the rest of the star's life. It decides which fuels burn next, the structure of white dwarfs, the mass of the black holes left by the heaviest stars, and the amounts of many elements thrown out in supernovae. For this reason the reaction is often called the most important one in nuclear astrophysics. It is also one of the hardest to measure: at the energies inside stars the reaction happens far too rarely for any experiment yet to detect it.", "details": "The stellar energy is near E = 300 keV, where the cross section is far below the sensitivity of any experiment so far. The S-factor is therefore extrapolated with multi-channel R-matrix fits from data above about 1 MeV. The ground-state capture is dominated by two components: E1 capture through the high-energy tail of the 1⁻ subthreshold state at 7.12 MeV interfering with the broad 1⁻ resonance at 9.6 MeV, and E2 capture through the 2⁺ subthreshold state at 6.92 MeV plus a direct contribution. Separating the two multipoles requires γ-ray angular distributions; the cascade transitions through the 6.05, 6.13, 6.92 and 7.12 MeV states add a few per cent at 300 keV but dominate at higher energies (deBoer et al. 2017).\n\nSurface experiments in forward kinematics with high-intensity α beams and Ge or BaF₂ arrays (Stuttgart, Karlsruhe) measured the E1 and E2 angular distributions; recoil separators (ERNA, DRAGON) measured the total cross section in inverse kinematics, independent of the γ-ray angular distribution. The review of deBoer et al. (2017) combined capture, scattering and β-delayed α-emission data in a global R-matrix analysis and gave the recommended rate used here. Its extrapolation is still debated: a ground-state ANC measured through ¹²C(¹¹B,⁷Li)¹⁶O gives a total rate up to 21% higher (Shen et al. 2023), and a time projection chamber in the γ beam of HIγS measured background-free angular distributions of the inverse reaction ¹⁶O(γ,α)¹²C, with an E1–E2 phase reported to agree with unitarity for the first time (Haverson et al. 2026).", "status": "uncertain", "statusNote": "No experiment has yet reached the energies at which helium burns in stars: the lowest data lie near 1 MeV, about three times higher. The stellar rate comes from extending the measured trend downwards with a nuclear model, and its uncertainty depends on how the reaction divides between its two main ways of emitting the γ-ray.", "statusPlain": "", "keywords": [], "methods": [ "direct-surface", "inverse-kinematics", "anc", "photonuclear", "theory" ], "measurements": [ { "year": 2001, "facility": "stuttgart-dynamitron", "lab": "", "method": "direct-surface", "energy": "E1 and E2 capture, forward kinematics", "note": "γ-ray angular distributions separated E1 and E2 ground-state capture; the derived rate is about 30% below the NACRE rate near 10⁸ K.", "refs": [ "kunz2001", "kunz2002", "hammer2005" ], "lowestKeV": null, "luna": false }, { "year": 2005, "facility": "erna", "lab": "", "method": "inverse-kinematics", "energy": "E = 1.9–4.9 MeV", "note": "First direct measurement of the total cross section: ¹⁶O recoils detected with the ERNA recoil separator behind a windowless helium gas target, with no γ-ray coincidence.", "refs": [ "schurmann2005" ], "lowestKeV": null, "luna": false }, { "year": 2006, "facility": "stuttgart-dynamitron", "lab": "", "method": "direct-surface", "energy": "E = 1.30–2.78 MeV", "note": "An array of nine EUROGAM HPGe detectors with BGO shields recorded the ground-state angular distributions at all angles at once, with α beams up to 340 µA on implanted ¹²C targets; E1 and E2 S-factors were derived with the mixing phase free or fixed from α + ¹²C scattering.", "refs": [ "assuncao2006" ], "lowestKeV": null, "luna": false }, { "year": 2006, "facility": "dragon", "lab": "", "method": "inverse-kinematics", "energy": "E = 2.2–5.42 MeV", "note": "Cascade through the 6.05 MeV 0⁺ state, measured with a BGO array in coincidence with recoils at the focal plane; S₆.₀(300 keV) = 25 (+16/−15) keV b, the largest cascade contribution.", "refs": [ "matei2006" ], "lowestKeV": null, "luna": false }, { "year": 2011, "facility": "erna", "lab": "", "method": "inverse-kinematics", "energy": "E = 3.3–4.5 MeV", "note": "The 6.05 MeV cascade was found to be pure E2 in this range; the extrapolation gives a negligible contribution at helium-burning energies, in contrast with the earlier DRAGON result.", "refs": [ "schurmann2011" ], "lowestKeV": null, "luna": false }, { "year": 2012, "facility": "karlsruhe-vdg", "lab": "", "method": "direct-surface", "energy": "E = 1.00–1.51 MeV", "note": "Nearly 4π BaF₂ array with a pulsed beam; the high efficiency allowed low beam currents, avoiding target degradation, and gave E1 and E2 components with accuracy comparable to the best Ge data.", "refs": [ "plag2012" ], "lowestKeV": null, "luna": false }, { "year": 2023, "facility": null, "lab": "Q3D magnetic spectrograph", "method": "anc", "energy": "¹⁶O ground state via ¹²C(¹¹B,⁷Li)¹⁶O", "note": "A new ground-state ANC, addressing a spread of more than two orders of magnitude among earlier values; the resulting total rate is up to 21% above deBoer et al. (2017), and in massive helium-core models it lowers the lower and upper edges of the black-hole mass gap by about 12% and 5%.", "refs": [ "shen2023" ], "lowestKeV": null, "luna": false }, { "year": 2026, "facility": null, "lab": "HIγS, Triangle Universities Nuclear Laboratory", "method": "photonuclear", "energy": "¹⁶O(γ,α)¹²C angular distributions", "note": "Background-free angular distributions of the time-reversed reaction, measured with a time projection chamber filled with N₂O gas; the measured E1–E2 mixing phase is reported to agree with the unitarity prediction for the first time.", "refs": [ "haverson2026" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "deboer2017", "angulo1999", "xu2013" ], "rmatrix": [], "openQuestions": [ "Direct data below 1 MeV, which need an underground accelerator able to deliver intense α beams, or high-intensity γ beams for the inverse reaction ¹⁶O(γ,α)¹²C.", "The E2 ground-state S-factor, whose extrapolation depends on the ANC of the 6.92 MeV subthreshold state and on the interference with the direct capture.", "The contribution of the 6.05 MeV cascade at low energy, where the DRAGON and ERNA analyses differ." ], "facts": [ { "text": "Black holes can measure this reaction: from the first ten black-hole mergers seen in gravitational waves, its S-factor at 300 keV must be above 175 keV b (68% confidence), if stellar models are right about the rest.", "refs": [ "farmer2020" ] } ], "related": [ "4He-aa-12C", "16O-ag-20Ne", "12C-12Ca-20Ne", "12C-12Cp-23Na" ], "q": { "value": 7.161917969999999, "annihilation": false, "kinetic": 7.161917969999999 }, "gamow": [ { "network": "he-burning", "label": "core helium burning", "T9": 0.2, "E0": 315.46054007794095, "width": 170.29006129301985 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "kunz2001", "kunz2002", "hammer2005", "schurmann2005", "assuncao2006", "matei2006", "schurmann2011", "plag2012", "shen2023", "haverson2026", "deboer2017", "angulo1999", "xu2013", "farmer2020" ], "luna": false, "lunaYears": [] }, { "id": "16O-ag-20Ne", "hasFile": true, "label": "¹⁶O(α,γ)²⁰Ne", "updated": null, "kind": "capture", "target": "16O", "projectile": "4He", "ejectile": "g", "product": "20Ne", "from": { "code": "16O", "A": 16, "Z": 8, "N": 8 }, "to": { "code": "20Ne", "A": 20, "Z": 10, "N": 10 }, "networks": [ "he-burning" ], "families": [ "he" ], "importance": "minor", "summary": "Oxygen-16 captures a helium nucleus and becomes neon-20. In helium burning it is slow, so most of the oxygen survives.", "role": "This is the last step of the chain of helium captures in helium burning. Because it is slow at the temperatures where helium burns, little oxygen turns into neon, and stars end helium burning with mostly carbon and oxygen. If the reaction were much faster, the oxygen made by the previous step would be lost to neon and the carbon-to-oxygen balance would change.", "details": "At helium-burning energies no resonance contributes significantly and the reaction proceeds mainly by direct capture, which makes the cross section very small. The rate is obtained from an R-matrix description of the low-energy resonances together with the direct-capture transitions (Costantini et al. 2010). DRAGON measured the total cross section at E = 2.26 MeV in inverse kinematics and determined, for the first time together, the total S-factor and its direct-capture components (Hager et al. 2011).", "status": "improving", "statusNote": "The rate rests on a direct-capture extrapolation from higher-energy data; no data reach the helium-burning energies.", "statusPlain": "", "keywords": [], "methods": [ "direct-surface", "inverse-kinematics" ], "measurements": [ { "year": 2010, "facility": null, "lab": "", "method": "direct-surface", "energy": "", "note": "New measurements of the low-energy resonances combined with earlier unpublished data in an R-matrix analysis, giving a rate for helium burning.", "refs": [ "costantini2010" ], "lowestKeV": null, "luna": false }, { "year": 2011, "facility": "dragon", "lab": "", "method": "inverse-kinematics", "energy": "E = 2.26 MeV", "note": "Total cross section from ²⁰Ne recoils; first determination of the total S-factor together with its direct-capture transitions.", "refs": [ "hager2011" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "angulo1999" ], "rmatrix": [], "openQuestions": [ "The direct-capture S-factor at energies below 1 MeV, where no measurement exists." ], "facts": [], "related": [ "12C-ag-16O" ], "q": { "value": 4.7298459699999995, "annihilation": false, "kinetic": 4.7298459699999995 }, "gamow": [ { "network": "he-burning", "label": "core helium burning", "T9": 0.2, "E0": 390.4594532151092, "width": 189.45442416534976 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "costantini2010", "hager2011", "angulo1999" ], "luna": false, "lunaYears": [] }, { "id": "14N-ag-18F", "hasFile": true, "label": "¹⁴N(α,γ)¹⁸F", "updated": null, "kind": "capture", "target": "14N", "projectile": "4He", "ejectile": "g", "product": "18F", "from": { "code": "14N", "A": 14, "Z": 7, "N": 7 }, "to": { "code": "18F", "A": 18, "Z": 9, "N": 9 }, "networks": [ "he-burning" ], "families": [ "he" ], "importance": "minor", "summary": "Nitrogen-14 captures a helium nucleus and becomes fluorine-18. It is the first step that turns the nitrogen left over from hydrogen burning into neon-22, the fuel of a stellar neutron source.", "role": "Hydrogen burning through the CNO cycle leaves most of a star's carbon, nitrogen and oxygen in the form of nitrogen-14. When helium starts to burn, this nitrogen captures helium and becomes fluorine-18, which decays within hours to oxygen-18. Oxygen-18 captures another helium nucleus and becomes neon-22. The amount of neon-22 that later releases neutrons is therefore set by the nitrogen that went through this reaction.", "details": "At helium-burning temperatures the rate is dominated by a few narrow resonances in ¹⁸F, and the compiled rates are sums of their strengths. Görres et al. (2000) measured the low-energy resonances with thin TiN targets and a Ge clover detector at Karlsruhe and Notre Dame. The lowest resonance was not observed; the authors argued that its strength lies far below the reach of present experiments.", "status": "improving", "statusNote": "The resonances that set the rate have been measured directly; the lowest one is known only from a theoretical argument.", "statusPlain": "", "keywords": [], "methods": [ "direct-surface" ], "measurements": [ { "year": 2000, "facility": null, "lab": "Forschungszentrum Karlsruhe, Karlsruhe, and University of Notre Dame", "method": "direct-surface", "energy": "low-energy resonances", "note": "Strengths of the low-energy resonances with thin TiN targets and a Ge clover detector; the lowest resonance was not observed and was argued to be far too weak to measure.", "refs": [ "gorres2000" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "angulo1999", "iliadis2010" ], "rmatrix": [], "openQuestions": [ "The strength of the lowest resonances, which control the rate at the start of helium burning." ], "facts": [], "related": [ "18F-bp-18O", "18O-ag-22Ne", "22Ne-an-25Mg", "14N-pg-15O" ], "q": { "value": 4.41523267, "annihilation": false, "kinetic": 4.41523267 }, "gamow": [ { "network": "he-burning", "label": "core helium burning", "T9": 0.2, "E0": 353.8756448865065, "width": 180.3607852471042 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": 6584.04, "stable": false, "text": "1.83 h" }, "references": [ "gorres2000", "angulo1999", "iliadis2010" ], "luna": false, "lunaYears": [] }, { "id": "18O-ag-22Ne", "hasFile": true, "label": "¹⁸O(α,γ)²²Ne", "updated": null, "kind": "capture", "target": "18O", "projectile": "4He", "ejectile": "g", "product": "22Ne", "from": { "code": "18O", "A": 18, "Z": 8, "N": 10 }, "to": { "code": "22Ne", "A": 22, "Z": 10, "N": 12 }, "networks": [ "he-burning" ], "families": [ "he" ], "importance": "minor", "summary": "Oxygen-18 captures a helium nucleus and becomes neon-22. It completes the conversion of nitrogen into neon-22 during helium burning.", "role": "The oxygen-18 made from nitrogen at the start of helium burning is turned into neon-22 by this reaction. Neon-22 later supplies neutrons in massive stars and in giant stars through ²²Ne(α,n)²⁵Mg. The speed of this reaction also decides how much oxygen-18 survives, which matters for the oxygen isotope ratios measured in stardust grains and in some carbon-rich stars.", "details": "The rate at helium-burning temperatures is dominated by two weak resonances at E(α,lab) ≈ 470 and 566 keV. For a long time only upper limits existed. Dababneh et al. (2003) gave the first partial strengths, 0.48 ± 0.16 µeV and 0.71 ± 0.17 µeV. Dombos et al. (2022) measured the total strengths for the first time at the CASPAR underground accelerator, with the γ-summing detector HECTOR: 0.26 ± 0.05 µeV and 0.63 ± 0.30 µeV for the resonances at 472 and 569 keV, with new strengths for those at 662.1, 749.9 and 767.6 keV. At the JUNA underground laboratory, Wang et al. (2023) fixed the energy of the lower of the two at E_α = 474.0 ± 1.1 keV and its spin and parity as 1⁻; a review of the work (Kajino 2023) quotes a strength of 0.25 ± 0.03 µeV.", "status": "improving", "statusNote": "The two resonances that dominate the rate have now been measured directly, the lower one in two underground laboratories, the higher one with a 50% uncertainty.", "statusPlain": "", "keywords": [], "methods": [ "direct-surface", "direct-underground" ], "measurements": [ { "year": 2003, "facility": null, "lab": "Forschungszentrum Karlsruhe, Karlsruhe", "method": "direct-surface", "energy": "E(α,lab) ≈ 470 and 566 keV resonances", "note": "First direct partial strengths of the two weak resonances, 0.48 ± 0.16 µeV and 0.71 ± 0.17 µeV.", "refs": [ "dababneh2003" ], "lowestKeV": null, "luna": false }, { "year": 2022, "facility": "caspar", "lab": "", "method": "direct-underground", "energy": "E(α,lab) = 472–768 keV", "note": "First total strengths of the 472 and 569 keV resonances, 0.26 ± 0.05 µeV and 0.63 ± 0.30 µeV, measured with the HECTOR γ-summing detector; new strengths for the resonances at 662.1, 749.9 and 767.6 keV.", "refs": [ "dombos2022" ], "lowestKeV": null, "luna": false }, { "year": 2023, "facility": "juna", "lab": "", "method": "direct-underground", "energy": "E(α,lab) = 470–787 keV", "note": "Energy of the key resonance E_α = 474.0 ± 1.1 keV, the first measurement this precise; the primary γ branchings fix Jπ = 1⁻, which removes the discrepancies between earlier strengths. The rate is up to about ten times more precise at 0.1–0.3 GK. A review of the result (Kajino 2023) quotes ωγ = 0.25 ± 0.03 µeV, a value not given in the abstract of the Letter.", "refs": [ "wang2023", "kajino2023" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "angulo1999", "iliadis2010" ], "rmatrix": [], "openQuestions": [ "The strength of the 569 keV resonance, known to 50%, and the agreement between the partial and total strengths of the 472 keV resonance." ], "facts": [ { "text": "Two underground laboratories, one in a former gold mine in South Dakota and one under a Chinese mountain, have measured the key resonance. The resonance strength measured in South Dakota, 0.26 ± 0.05 µeV, agrees within its uncertainty with the 0.25 ± 0.03 µeV that a review quotes for the Chinese measurement.", "refs": [ "dombos2022", "kajino2023" ] } ], "related": [ "14N-ag-18F", "18F-bp-18O", "22Ne-an-25Mg", "22Ne-ag-26Mg" ], "q": { "value": 9.66681557, "annihilation": false, "kinetic": 9.66681557 }, "gamow": [ { "network": "he-burning", "label": "core helium burning", "T9": 0.2, "E0": 393.4041290262004, "width": 190.16747385261618 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "dababneh2003", "dombos2022", "wang2023", "kajino2023", "angulo1999", "iliadis2010" ], "luna": false, "lunaYears": [] }, { "id": "12C-12Ca-20Ne", "hasFile": true, "label": "¹²C(¹²C,α)²⁰Ne", "updated": null, "kind": "fusion", "target": "12C", "projectile": "12C", "ejectile": "4He", "product": "20Ne", "from": { "code": "12C", "A": 12, "Z": 6, "N": 6 }, "to": { "code": "20Ne", "A": 20, "Z": 10, "N": 10 }, "networks": [ "carbon-burning" ], "families": [ "carbon" ], "importance": "key", "summary": "Two carbon nuclei fuse, and the compound nucleus breaks up into neon-20 and a helium nucleus. This is the main way carbon burns in stars.", "role": "When a star of more than about eight solar masses has used up its helium, its core is mostly carbon and oxygen. The core contracts and heats until carbon nuclei collide hard enough to fuse. Each fusion makes a highly excited magnesium-24, which at once falls apart, most often into neon-20 and an alpha particle or into sodium-23 and a proton. The neon left by this branch is the fuel of the next stage, neon burning. How fast carbon fuses decides how long carbon burning lasts, how hot it must be, and so the inner structure of the star before it explodes. The same reaction starts the explosion of a white dwarf in a type Ia supernova and the rare, long X-ray flashes called superbursts on neutron stars. Its rate at stellar energies is still uncertain: experiments disagree by large factors.", "details": "¹²C + ¹²C forms ²⁴Mg at an excitation energy of about 13.9 MeV plus the centre-of-mass energy, which decays mainly by α emission to ²⁰Ne and by proton emission to ²³Na; the neutron channel to ²³Mg is closed below 2.6 MeV. The Gamow window for core carbon burning in a 15 M☉ star (0.83 GK) spans about 1.7–2.6 MeV, with its peak at 2.1 MeV; at the ignition of a superburst on an accreting neutron star, near 0.5 GK (Cooper et al. 2009), it moves down to about 1.2–1.8 MeV. Unlike most heavy-ion systems, the excitation function shows pronounced resonant structure down to the lowest measured energies, which makes any extrapolation from the data uncertain (Spillane et al. 2007; Zickefoose et al. 2018; Morales-Gallegos et al. 2024). The cross section of the neighbouring system ¹²C + ¹³C, which has no such resonances, has been used to set an upper limit on the non-resonant part (Zhang et al. 2020).\n\nThe excitation function is conventionally shown as the modified S-factor S*(E) = σ(E) E exp(87.21/√E + 0.46 E), with E in MeV, which removes most of the strong energy dependence that remains in the ordinary S-factor of this heavy system; the standard rate of Caughlan and Fowler (1988) assumes a constant S* below the data.\n\nBelow the data, two descriptions of the non-resonant trend compete. The fusion-hindrance model (Jiang et al. 2007) predicts that the S-factor passes through a maximum and falls at deep sub-barrier energies; the rates of Jiang et al. (2018) and Monpribat et al. (2022) are built on it, as alternatives to the standard rate of Caughlan and Fowler (1988). The particle–γ coincidence measurements at Orsay (STELLA, Fruet et al. 2020; Nippert et al. 2025) and at Notre Dame (Tan et al. 2020) remove most of the background from hydrogen and deuterium in the target that limited earlier singles measurements; the STELLA data support the hindrance trend. A refit of the same data sets with a free exponent in the logarithmic-slope parametrization finds no hindrance (Uzawa and Hagino 2025), so the question remains open.\n\nThe Trojan Horse measurement of Tumino et al. (2018), through ¹²C(¹⁴N,α²⁰Ne)²H and ¹²C(¹⁴N,p²³Na)²H in quasi-free kinematics, reported resonances between 0.8 and 2.7 MeV that raise the rate by more than a factor of 25 near 0.5 GK. Mukhamedzhanov et al. (2019) argued that the rise is an artefact of the plane-wave approximation used in the analysis and disappears when Coulomb–nuclear distortions are included; the direct coincidence data of Tan et al. (2020) disagree strongly with the Trojan Horse result. A possible physical origin for low-energy resonances is a set of 0⁺ states of ²⁴Mg near the ¹²C + ¹²C threshold, found in ²⁴Mg(α,α′) and decaying mostly to ²⁰Ne + α, which may be ¹²C + ¹²C cluster states playing a role like the Hoyle state's in helium burning (Adsley et al. 2022). LUNA is preparing a direct measurement of the γ-rays from the α and p channels at the underground Bellotti Ion Beam Facility, with an HPGe detector inside an active NaI(Tl) veto (Gesuè et al. 2025).", "status": "uncertain", "statusNote": "Direct measurements reach only the upper part of the energies at which carbon burns in massive stars, and the measured cross section is full of resonances. The ways of extending it downwards, and an indirect measurement that reaches those energies, disagree by orders of magnitude.", "statusPlain": "", "keywords": [ "12C+12C", "12C12C", "C+C", "carbon fusion", "carbon burning" ], "methods": [ "direct-surface", "thm", "theory" ], "measurements": [ { "year": 1969, "facility": null, "lab": "", "method": "direct-surface", "energy": "down to E ≈ 2.5 MeV", "note": "Early measurements of the α and p channels, by charged-particle or γ-ray spectroscopy (High and Čujec recorded the γ-rays at 90° and 270°; Becker et al. detected the particles); together they covered the cross section down to about 2.5 MeV.", "refs": [ "patterson1969", "mazarakis1973", "high1977", "becker1981" ], "lowestKeV": null, "luna": false }, { "year": 2006, "facility": null, "lab": "", "method": "direct-surface", "energy": "", "note": "γ-ray measurement of the α and p channels, aimed at bringing the earlier, mutually inconsistent data sets into agreement.", "refs": [ "aguilera2006" ], "lowestKeV": null, "luna": false }, { "year": 2007, "facility": "bochum", "lab": "", "method": "direct-surface", "energy": "E = 2.10–4.75 MeV", "note": "γ-ray spectroscopy with thick carbon targets whose hydrogen contamination was made very low. A strong resonance at 2.14 MeV, at the Gamow peak of core carbon burning (0.83 GK) and above the window of superburst ignition (0.5 GK), raises the α-channel rate by about a factor of five near 0.8 GK.", "refs": [ "spillane2007" ], "lowestKeV": null, "luna": false }, { "year": 2018, "facility": "lns-catania", "lab": "", "method": "thm", "energy": "E = 0.8–2.7 MeV, from ¹²C(¹⁴N,α²⁰Ne)²H", "note": "Several resonances across the Gamow window; the combined α and p rate is more than 25 times the reference rate near 0.5 GK. The analysis was disputed by Mukhamedzhanov et al. (2019), who found that the rise disappears once Coulomb–nuclear distortions are included.", "refs": [ "tumino2018", "mukhamedzhanov2019" ], "lowestKeV": null, "luna": false }, { "year": 2020, "facility": "andromede", "lab": "", "method": "direct-surface", "energy": "into the Gamow window of massive stars", "note": "STELLA: particle–γ coincidences between the silicon array and LaBr₃ detectors, with a rotating target, remove the ambiguities of γ-only or particle-only measurements. The data span more than eight orders of magnitude and support the fusion-hindrance model.", "refs": [ "fruet2020", "heine2018" ], "lowestKeV": null, "luna": false }, { "year": 2020, "facility": "notre-dame", "lab": "", "method": "direct-surface", "energy": "thick-target yield in 50 keV steps", "note": "Particle–γ coincidences with the SAND silicon array at the 5U Pelletron on highly ordered pyrolytic graphite targets. The results disagree strongly with the Trojan Horse measurement.", "refs": [ "tan2020" ], "lowestKeV": null, "luna": false }, { "year": 2020, "facility": null, "lab": "", "method": "activation", "energy": "¹²C + ¹³C down to E = 2.32 MeV", "note": "Not ¹²C + ¹²C itself: ¹²C(¹³C,p)²⁴Na measured by counting the ²⁴Na activity in an underground counting laboratory. Models normalized to these data give an upper limit on the non-resonant ¹²C + ¹²C cross section at stellar energies and argue against the S-factor maximum of the hindrance model.", "refs": [ "zhang2020" ], "lowestKeV": null, "luna": false }, { "year": 2022, "facility": "circe", "lab": "", "method": "direct-surface", "energy": "E = 2.51–4.36 MeV", "note": "Protons and α particles identified with ΔE–E telescopes, in steps of 10–25 keV. The branching ratios of the individual proton and α groups change strongly with energy, and the angular distributions (three angles) are not isotropic, a possible cause of the disagreement between data sets. A first journal article (Eur. Phys. J. A 58, 65, 2022) was retracted (Eur. Phys. J. A 59, 120, 2023) because of an error in the script that computed the beam energy loss; the corrected article (Eur. Phys. J. A 60, 2024) keeps the general conclusions.", "refs": [ "moralesgallegos2022", "moralesgallegos2023r", "moralesgallegos2024" ], "lowestKeV": null, "luna": false }, { "year": 2025, "facility": "andromede", "lab": "", "method": "direct-surface", "energy": "E ≈ 2.2–2.6 MeV; 3.23 MeV", "note": "Refined STELLA excitation function near its lowest coincidence points: a lower average S-factor than standard extrapolations between 2.2 and 2.6 MeV, and no confirmation of an overall rise of the S-factor at deep sub-barrier energies.", "refs": [ "nippert2025" ], "lowestKeV": null, "luna": false }, { "year": 2026, "facility": null, "lab": "HI-13 tandem accelerator, China Institute of Atomic Energy, Beijing", "method": "thm", "energy": "Gamow window, resonances near 1.5 MeV", "note": "An independent Trojan Horse measurement with ¹⁶O, not ¹⁴N, as the Trojan horse nucleus and the spectator α detected near 0°, which the authors describe as a first for the method; their analysis, DWBA-based as they describe it, gives resonances near 1.5 MeV in both the α₀ and α₁ channels. A preprint argues that the plane-wave approximation behind the analysis breaks down once Coulomb distortions are included (Mukhamedzhanov 2026); no reply has appeared yet.", "refs": [ "li2026", "mukhamedzhanov2026" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "caughlan1988", "jiang2018", "monpribat2022" ], "rmatrix": [], "openQuestions": [ "Whether the S-factor falls at deep sub-barrier energies (fusion hindrance) or keeps rising; the answer depends on fitting choices and on which of the many data sets are used.", "Whether resonances below 2 MeV exist and how strong they are, as the Trojan Horse analysis suggests and its critics dispute.", "Direct data below 2.1 MeV, the aim of the underground LUNA campaign." ], "facts": [], "related": [ "12C-12Cp-23Na", "12C-12Cn-23Mg", "12C-ag-16O", "23Na-pa-20Ne" ], "q": { "value": 4.61701633, "annihilation": false, "kinetic": 4.61701633 }, "gamow": [ { "network": "carbon-burning", "label": "core carbon burning, 15 M☉ star", "T9": 0.83, "E0": 2134.669489844589, "width": 902.4146774717461 }, { "network": "carbon-burning", "label": "superburst ignition, accreting neutron star", "T9": 0.5, "E0": 1522.6213584739937, "width": 591.5381294065413 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "patterson1969", "mazarakis1973", "high1977", "becker1981", "aguilera2006", "spillane2007", "tumino2018", "mukhamedzhanov2019", "fruet2020", "heine2018", "tan2020", "zhang2020", "moralesgallegos2022", "moralesgallegos2023r", "moralesgallegos2024", "nippert2025", "li2026", "mukhamedzhanov2026", "caughlan1988", "jiang2018", "monpribat2022", "jiang2007", "uzawa2025", "gesue2025", "cooper2009", "adsley2022" ], "luna": false, "lunaYears": [] }, { "id": "12C-12Cp-23Na", "hasFile": true, "label": "¹²C(¹²C,p)²³Na", "updated": null, "kind": "fusion", "target": "12C", "projectile": "12C", "ejectile": "1H", "product": "23Na", "from": { "code": "12C", "A": 12, "Z": 6, "N": 6 }, "to": { "code": "23Na", "A": 23, "Z": 11, "N": 12 }, "networks": [ "carbon-burning" ], "families": [ "carbon" ], "importance": "key", "summary": "Two carbon nuclei fuse, and the compound nucleus breaks up into sodium-23 and a proton. Together with the branch to neon-20, it is how carbon burns in stars.", "role": "Carbon fusion has two main outcomes: neon-20 with an alpha particle, and sodium-23 with a proton. This branch makes sodium. The protons it frees do not survive long in the hot core: they are captured by the nuclei around them, and on sodium-23 they make neon-20 or magnesium-24. The balance between the two branches, and how fast carbon fuses at all, sets how much sodium and neon a massive star leaves behind. Measuring the reaction at the energies of a stellar core is very hard, and the results of different methods still disagree by large factors.", "details": "The proton channel (Q = 2.24 MeV) is measured either by detecting the protons, whose spectrum resolves the ²³Na final states, or through the γ rays of ²³Na, mainly the 440 keV line from its first excited state, which cannot see the decays that feed the ground state directly. Hydrogen and deuterium in the carbon target produce a beam-induced background that dominates singles measurements at the lowest energies (Zickefoose et al. 2018). Particle–γ coincidences (Fruet et al. 2020; Tan et al. 2020; Nippert et al. 2025) select the protons in coincidence with the de-excitation γ-rays and suppress this background, at the cost of the ground-state branch, which must be inferred.\n\nThe excitation function shows resonances down to about 2.1 MeV (Spillane et al. 2007; Zickefoose et al. 2018), with branching ratios of the individual proton groups that change strongly from one energy to the next (Morales-Gallegos et al. 2024). The Gamow window spans about 1.7–2.6 MeV for core carbon burning at 0.83 GK and about 1.2–1.8 MeV for superburst ignition near 0.5 GK (Cooper et al. 2009), so direct data cover only the upper half of the first and none of the second. Below the data the same questions apply as for the α channel: fusion hindrance or a rising S-factor, and the disputed Trojan Horse resonances (Tumino et al. 2018; Mukhamedzhanov et al. 2019). The p channel also serves as the mirror reference for extrapolating the n channel, ¹²C(¹²C,n)²³Mg (Bucher et al. 2015). LUNA is preparing a direct measurement of the γ-rays of the p and α channels below 2.1 MeV at the underground Bellotti Ion Beam Facility, with an HPGe detector inside an active NaI(Tl) veto (Gesuè et al. 2025).", "status": "uncertain", "statusNote": "The measured cross section is full of resonances, direct data reach only the upper part of the energies that matter in stars, and the ways of extending them downwards disagree by orders of magnitude.", "statusPlain": "", "keywords": [ "12C+12C", "12C12C", "C+C", "carbon fusion", "carbon burning" ], "methods": [ "direct-surface", "thm", "theory" ], "measurements": [ { "year": 1969, "facility": null, "lab": "", "method": "direct-surface", "energy": "down to E ≈ 2.5 MeV", "note": "Early measurements of the α and p channels by charged-particle or γ-ray spectroscopy; together they covered the cross section down to about 2.5 MeV.", "refs": [ "patterson1969", "mazarakis1973", "high1977", "becker1981" ], "lowestKeV": null, "luna": false }, { "year": 2006, "facility": null, "lab": "", "method": "direct-surface", "energy": "", "note": "γ-ray measurement of the α and p channels, aimed at bringing the earlier, mutually inconsistent data sets into agreement.", "refs": [ "aguilera2006" ], "lowestKeV": null, "luna": false }, { "year": 2007, "facility": "bochum", "lab": "", "method": "direct-surface", "energy": "E = 2.10–4.75 MeV", "note": "γ-ray spectroscopy of both channels on targets with very low hydrogen contamination; new resonances at and below 3 MeV, the strongest at 2.14 MeV.", "refs": [ "spillane2007" ], "lowestKeV": null, "luna": false }, { "year": 2018, "facility": null, "lab": "", "method": "direct-surface", "energy": "E = 2.00–4.00 MeV", "note": "Proton spectroscopy: broad resonances above 3.00 MeV, and data compatible with the resonance structure near 2.1 MeV. The low-energy points are limited by count rate and possible background from hydrogen in the target; the authors judge any extrapolation highly uncertain.", "refs": [ "zickefoose2018" ], "lowestKeV": null, "luna": false }, { "year": 2018, "facility": "lns-catania", "lab": "", "method": "thm", "energy": "E = 0.8–2.7 MeV, from ¹²C(¹⁴N,p²³Na)²H", "note": "Several resonances across the Gamow window and a combined rate more than 25 times the reference rate near 0.5 GK; disputed by Mukhamedzhanov et al. (2019).", "refs": [ "tumino2018", "mukhamedzhanov2019" ], "lowestKeV": null, "luna": false }, { "year": 2020, "facility": "andromede", "lab": "", "method": "direct-surface", "energy": "into the Gamow window of massive stars", "note": "STELLA particle–γ coincidences; the data support the fusion-hindrance model.", "refs": [ "fruet2020", "heine2018" ], "lowestKeV": null, "luna": false }, { "year": 2020, "facility": "notre-dame", "lab": "", "method": "direct-surface", "energy": "thick-target yield in 50 keV steps", "note": "SAND particle–γ coincidences; strong disagreement with the Trojan Horse result.", "refs": [ "tan2020" ], "lowestKeV": null, "luna": false }, { "year": 2020, "facility": null, "lab": "", "method": "activation", "energy": "¹²C + ¹³C down to E = 2.32 MeV", "note": "Not ¹²C + ¹²C itself: ¹²C(¹³C,p)²⁴Na measured by counting the ²⁴Na activity in an underground counting laboratory. Models normalized to these data give an upper limit on the non-resonant ¹²C + ¹²C cross section at stellar energies and argue against the S-factor maximum of the hindrance model.", "refs": [ "zhang2020" ], "lowestKeV": null, "luna": false }, { "year": 2022, "facility": "circe", "lab": "", "method": "direct-surface", "energy": "E = 2.51–4.36 MeV", "note": "Protons and α particles identified with ΔE–E telescopes, in steps of 10–25 keV. The branching ratios of the individual proton and α groups change strongly with energy, and the angular distributions (three angles) are not isotropic, a possible cause of the disagreement between data sets. A first journal article (Eur. Phys. J. A 58, 65, 2022) was retracted (Eur. Phys. J. A 59, 120, 2023) because of an error in the script that computed the beam energy loss; the corrected article (Eur. Phys. J. A 60, 2024) keeps the general conclusions.", "refs": [ "moralesgallegos2022", "moralesgallegos2023r", "moralesgallegos2024" ], "lowestKeV": null, "luna": false }, { "year": 2025, "facility": "andromede", "lab": "", "method": "direct-surface", "energy": "E ≈ 2.2–2.6 MeV; 3.23 MeV", "note": "Refined STELLA excitation function: a lower average S-factor than standard extrapolations between 2.2 and 2.6 MeV, and at 3.23 MeV a ratio of only about 2% between the proton and α branches to the first excited states.", "refs": [ "nippert2025" ], "lowestKeV": null, "luna": false }, { "year": 2026, "facility": null, "lab": "HI-13 tandem accelerator, China Institute of Atomic Energy, Beijing", "method": "thm", "energy": "Gamow window, resonances near 1.5 MeV", "note": "Preprint. The same ¹⁶O-breakup technique as for the α channel shows resonant structure near 1.5 MeV in the p₀ and p₁ channels and no hindrance in the measured range; the trend is qualitatively like that of Tumino et al. (2018) and unlike the modified analysis of Mukhamedzhanov et al. (2019).", "refs": [ "li2026b" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "caughlan1988", "jiang2018", "monpribat2022" ], "rmatrix": [], "openQuestions": [ "The ground-state proton branch, which γ-ray and coincidence measurements do not see directly.", "The p/α branching at the energies of carbon burning, which decides the sodium yield.", "Whether the S-factor falls (fusion hindrance) or keeps rising below the data." ], "facts": [], "related": [ "12C-12Ca-20Ne", "12C-12Cn-23Mg", "23Na-pa-20Ne", "23Na-pg-24Mg", "12C-ag-16O" ], "q": { "value": 2.2408824359999997, "annihilation": false, "kinetic": 2.2408824359999997 }, "gamow": [ { "network": "carbon-burning", "label": "core carbon burning, 15 M☉ star", "T9": 0.83, "E0": 2134.669489844589, "width": 902.4146774717461 }, { "network": "carbon-burning", "label": "superburst ignition, accreting neutron star", "T9": 0.5, "E0": 1522.6213584739937, "width": 591.5381294065413 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "patterson1969", "mazarakis1973", "high1977", "becker1981", "aguilera2006", "spillane2007", "zickefoose2018", "tumino2018", "mukhamedzhanov2019", "fruet2020", "heine2018", "tan2020", "zhang2020", "moralesgallegos2022", "moralesgallegos2023r", "moralesgallegos2024", "nippert2025", "li2026b", "caughlan1988", "jiang2018", "monpribat2022", "jiang2007", "uzawa2025", "gesue2025", "cooper2009", "adsley2022" ], "luna": false, "lunaYears": [] }, { "id": "12C-12Cn-23Mg", "hasFile": true, "label": "¹²C(¹²C,n)²³Mg", "updated": null, "kind": "fusion", "target": "12C", "projectile": "12C", "ejectile": "n", "product": "23Mg", "from": { "code": "12C", "A": 12, "Z": 6, "N": 6 }, "to": { "code": "23Mg", "A": 23, "Z": 12, "N": 11 }, "networks": [ "carbon-burning" ], "families": [ "carbon" ], "importance": "minor", "summary": "A rare outcome of carbon fusion: magnesium-23 and a neutron. It needs extra energy, so it happens only in the hottest carbon-burning environments.", "role": "Unlike the two main branches, this one takes energy instead of releasing it: the colliding carbon nuclei must bring in at least about 2.6 MeV between them. At the temperatures of ordinary carbon burning very few collisions are that energetic, so the branch is small. It matters for the elements made where carbon burns hotter: in the explosions of the very massive first stars it helps set how much sodium and aluminium is made. The magnesium-23 it makes is radioactive and decays within seconds to sodium-23. Direct measurements have reached the energies at which it operates in stars.", "details": "The channel is endothermic (Q = −2.60 MeV) and closed below that energy, so the ordinary Gamow window (2.1 ± 0.45 MeV at 0.83 GK) lies almost entirely below threshold: the energies that contribute start at 2.60 MeV and fall off within a few hundred keV, as the Boltzmann factor drops faster than the Coulomb penetration rises (the range shown in the facts box). Bucher et al. (2015) measured it directly at the Notre Dame FN tandem into the astrophysical energy range, with a neutron detector whose efficiency was simulated and checked with monoenergetic neutrons, and cross-checked the cross section by counting the ²³Mg activity. Their extrapolation to lower energies uses data on the mirror proton channel, ¹²C(¹²C,p)²³Na; they quote a rate uncertainty smaller than astrophysical models require, and find the channel important for sodium and aluminium production in Population III pair-instability supernovae, and non-negligible for the weak s-process and for ⁶⁰Fe.\n\nIn carbon-shell burning the main neutron source of the weak s-process is ²²Ne(α,n)²⁵Mg, with the α particles supplied by ¹²C(¹²C,α)²⁰Ne; the n channel adds neutrons directly, and how much depends on its share of the total rate. Pignatari et al. (2013) followed the s-process and p-process yields of a 25 M☉ star with the total rate and the three channels varied, and found them sensitive to both.", "status": "improving", "statusNote": "A direct measurement has reached stellar energies, and the extrapolation below it leans on the better-measured proton channel; how far that holds depends on the same open questions as carbon fusion as a whole.", "statusPlain": "", "keywords": [ "12C+12C", "12C12C", "C+C", "carbon fusion", "carbon burning" ], "methods": [ "direct-surface", "activation" ], "measurements": [ { "year": 2015, "facility": "notre-dame", "lab": "", "method": "direct-surface", "energy": "deep into the astrophysical energy range", "note": "First direct measurement at stellar energies, by neutron counting checked against the ²³Mg activity; the extrapolation uses the mirror reaction ¹²C(¹²C,p)²³Na.", "refs": [ "bucher2015" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "caughlan1988" ], "rmatrix": [], "openQuestions": [ "The validity of the mirror-channel extrapolation, which inherits the resonance structure and the hindrance question of ¹²C(¹²C,p)²³Na." ], "facts": [], "related": [ "12C-12Cp-23Na", "12C-12Ca-20Ne" ], "q": { "value": -2.597648099999999, "annihilation": false, "kinetic": -2.597648099999999 }, "gamow": [ { "network": "carbon-burning", "label": "core carbon burning, 15 M☉ star", "T9": 0.83, "E0": 2597.648099999999, "width": 236.78493987968568, "lo": 2597.648099999999, "hi": 2834.4330398796847, "threshold": 2597.648099999999, "thresholdLimited": true }, { "network": "carbon-burning", "label": "superburst ignition, accreting neutron star", "T9": 0.5, "E0": 2597.648099999999, "width": 76.83863244792656, "lo": 2597.648099999999, "hi": 2674.4867324479255, "threshold": 2597.648099999999, "thresholdLimited": true } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": 11.3039, "stable": false, "text": "11.3 s" }, "references": [ "bucher2015", "caughlan1988", "pignatari2013" ], "luna": false, "lunaYears": [] }, { "id": "13C-an-16O", "hasFile": true, "label": "¹³C(α,n)¹⁶O", "updated": null, "kind": "transfer", "target": "13C", "projectile": "4He", "ejectile": "n", "product": "16O", "from": { "code": "13C", "A": 13, "Z": 6, "N": 7 }, "to": { "code": "16O", "A": 16, "Z": 8, "N": 8 }, "networks": [ "neutron-sources" ], "families": [ "neutrons" ], "importance": "key", "summary": "Carbon-13 captures a helium nucleus and releases a free neutron. In stars like the Sun near the end of their lives, this reaction supplies the neutrons that build about half the nuclei heavier than iron.", "role": "Elements heavier than iron are made mostly by adding neutrons to existing nuclei. In the slow neutron-capture process, or s-process, the neutrons arrive one at a time, slowly enough that unstable nuclei usually decay before the next one comes. In low-mass stars on the asymptotic giant branch (AGB stars, the last bright phase of stars like the Sun), a thin layer rich in carbon-13 forms between helium flashes. There this reaction releases neutrons at a temperature of about 90 million kelvin, and their number decides how much strontium, barium, lead and many other elements the star makes. The same reaction may also drive the faster intermediate process, or i-process, when hydrogen is mixed into hot helium-burning layers.", "details": "At T₉ ≈ 0.09 the Gamow window lies roughly between 140 and 230 keV, where the cross section is dominated by the high-energy tail of the 1/2⁺ state at 6.356 MeV in ¹⁷O, about 3 keV below the α threshold. Its contribution depends on the reduced α width, usually expressed through the asymptotic normalization coefficient (ANC), and on the exact position of the state relative to the threshold (deBoer et al. 2020). Indirect methods, the Trojan Horse method (La Cognata et al. 2012) and α-transfer ANC measurements (Avila et al. 2015), constrain this state, but their results have not always agreed. Avila et al. removed the disagreement among the α-transfer measurements, while a difference from the Trojan Horse value remained.\n\nAt the surface, the low event rate against the neutron background kept direct measurements above the Gamow window. The LUNA measurement under Gran Sasso reached E = 230–300 keV, reaching the upper edge of the s-process Gamow window (230 keV) for the first time (the authors describe it as inside the Gamow peak), with much smaller uncertainties than earlier data (Ciani et al. 2021). The JUNA measurement in the China Jinping Underground Laboratory, combined with data taken at Sichuan University, covered 0.24–1.9 MeV in one consistent data set and constrained the near-threshold state directly (Gao et al. 2022). At higher energies, the first accurate differential cross sections below 1 MeV, at 18 angles from 0.8 to 6.5 MeV, resolve long-standing differences between the earlier data and, in an R-matrix fit, could bring the uncertainty of the extrapolation to about 5% (deBoer et al. 2024).", "status": "improving", "statusNote": "Measurements deep underground now reach the upper part of the energy range that matters in giant stars, from 230 keV up. Below that, the rate still depends on extending the data with a model of a nuclear state that lies just below the reaction threshold.", "statusPlain": "", "keywords": [], "methods": [ "direct-underground", "direct-surface", "thm", "anc" ], "measurements": [ { "year": 1993, "facility": null, "lab": "", "method": "direct-surface", "energy": "", "note": "Direct measurement of both s-process neutron sources, ¹³C(α,n)¹⁶O and ²²Ne(α,n)²⁵Mg, with new rates for each.", "refs": [ "drotleff1993" ], "lowestKeV": null, "luna": false }, { "year": 2008, "facility": null, "lab": "Forschungszentrum Karlsruhe, Karlsruhe", "method": "direct-surface", "energy": "", "note": "Direct measurement and R-matrix analysis of the cross section; the resulting rate became the reference for later comparisons.", "refs": [ "heil2008" ], "lowestKeV": null, "luna": false }, { "year": 2012, "facility": null, "lab": "", "method": "thm", "energy": "quasi-free ¹³C(⁶Li,n¹⁶O)d", "note": "First Trojan Horse study of the −3 keV subthreshold resonance from the 6.356 MeV level of ¹⁷O, which dominates the cross section in the 140–230 keV window.", "refs": [ "lacognata2012" ], "lowestKeV": null, "luna": false }, { "year": 2015, "facility": null, "lab": "John D. Fox Accelerator Laboratory, Florida State University, Tallahassee", "method": "anc", "energy": "⁶Li(¹³C,d)¹⁷O at sub-Coulomb energy, 8 MeV ¹³C beam", "note": "Squared Coulomb-modified α ANC of the 1/2⁺ state at 6.356 MeV, 3.6 ± 0.7 fm⁻¹. The result removes the disagreement between earlier α-transfer measurements; some disagreement with the Trojan Horse result remains.", "refs": [ "avila2015" ], "lowestKeV": null, "luna": false }, { "year": 2021, "facility": "luna-400", "lab": "", "method": "direct-underground", "energy": "E = 230–300 keV", "note": "First direct data reaching the upper edge of the s-process Gamow window (230 keV), measured deep underground with much smaller uncertainties than previous data; stellar models with the revised rate change the yields of ⁶⁰Fe, ²⁰⁵Pb and ¹⁵²Gd in stars of near-solar composition.", "refs": [ "ciani2021" ], "lowestKeV": null, "luna": true }, { "year": 2022, "facility": "juna", "lab": "", "method": "direct-underground", "energy": "E = 0.24–1.9 MeV (with Sichuan University above ground)", "note": "One consistent data set across the s- and i-process windows; the uncertainty at the centre of the i-process window fell from about 60% to 15%, with the first direct determination of the α strength of the near-threshold state.", "refs": [ "gao2022" ], "lowestKeV": null, "luna": false }, { "year": 2023, "facility": null, "lab": "Edwards Accelerator Laboratory, Ohio University", "method": "direct-surface", "energy": "E_α = 2.9–8.0 MeV", "note": "Total cross section with a ³He–BF₃ neutron barrel: considerably lower than earlier direct data above E_α = 5 MeV, as corrections based on Hauser–Feshbach estimates had suggested; Hauser–Feshbach branchings do not reproduce the earlier partial-channel data.", "refs": [ "brandenburg2023" ], "lowestKeV": null, "luna": false }, { "year": 2024, "facility": "notre-dame", "lab": "", "method": "direct-surface", "energy": "E_α = 0.8–6.5 MeV, 18 angles (α,n₀)", "note": "Differential cross section of the (α,n₀) channel at angles from 0 to 160°, over 700 angular distributions, the first accurate ones below 1 MeV; added to the R-matrix fit, they suggest an extrapolation uncertainty of about 5%, against about 15% before.", "refs": [ "deboer2024" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "angulo1999", "xu2013", "deboer2020" ], "rmatrix": [], "openQuestions": [ "The ANC and the exact energy of the 1/2⁺ state at 6.356 MeV in ¹⁷O, which control the extrapolation below 230 keV.", "Absolute normalization of the direct data, which depends on target stoichiometry under beam and on the neutron-detection efficiency as a function of neutron energy and angle.", "Consistent data over a wide energy range, overlapping the underground and surface measurements, to constrain the R-matrix fit." ], "facts": [ { "text": "The neutron source of the s-process also matters for dark-matter and neutrino detectors, whose neutron backgrounds are estimated from its yields. For alpha particles above 6 MeV, the neutron yields inferred from the 2023 data are noticeably higher than those used in detector-background estimates.", "refs": [ "brandenburg2023" ] } ], "related": [ "13C-pg-14N", "22Ne-an-25Mg", "17O-an-20Ne" ], "q": { "value": 2.2156091700000005, "annihilation": false, "kinetic": 2.2156091700000005 }, "gamow": [ { "network": "neutron-sources", "label": "AGB ¹³C pocket", "T9": 0.09, "E0": 186.45525109529186, "width": 87.82342031104837 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "drotleff1993", "heil2008", "lacognata2012", "avila2015", "ciani2021", "gao2022", "brandenburg2023", "deboer2024", "angulo1999", "xu2013", "deboer2020" ], "luna": true, "lunaYears": [ 2021 ] }, { "id": "22Ne-an-25Mg", "hasFile": true, "label": "²²Ne(α,n)²⁵Mg", "updated": null, "kind": "transfer", "target": "22Ne", "projectile": "4He", "ejectile": "n", "product": "25Mg", "from": { "code": "22Ne", "A": 22, "Z": 10, "N": 12 }, "to": { "code": "25Mg", "A": 25, "Z": 12, "N": 13 }, "networks": [ "neutron-sources" ], "families": [ "neutrons" ], "importance": "key", "summary": "Neon-22 captures a helium nucleus and releases a neutron. It is the main neutron source in massive stars and a second source in the late pulses of giant stars.", "role": "Stars convert the carbon, nitrogen and oxygen they were born with into nitrogen-14 while they burn hydrogen. When helium burns, the nitrogen turns into neon-22. Near the end of helium burning in stars more than about ten times the mass of the Sun, and during the hottest helium flashes of giant stars, the temperature rises enough for neon-22 to capture a helium nucleus and release a neutron. These neutrons make most of the elements between iron and strontium, the weak s-process. Releasing a neutron costs energy, so the reaction cannot happen at all below a threshold. Below it, and in competition above it, neon-22 can capture helium through another reaction, ²²Ne(α,γ)²⁶Mg, which uses it up without giving a neutron. The balance between the two decides how many neutrons are released.", "details": "The reaction opens just above the neutron threshold, and the rate at T₉ ≈ 0.2–0.3 is dominated by resonances in ²⁶Mg above it, in particular the well-known resonance at 830 keV (E_α,lab; E_cm ≈ 702 keV). Below it, direct experiments give only upper limits, because the cross section is small and the neutron background in surface laboratories is large. The rate therefore rests on the properties of near-threshold ²⁶Mg states obtained indirectly: neutron resonances in ²⁵Mg + n measured at n_TOF (Massimi et al. 2017), α-transfer reactions (Ota et al. 2020; Jayatissa et al. 2020). The evaluation of Adsley et al. (2021), based on updated spin-parity assignments, lowered the (α,n) rate substantially while leaving the (α,γ) rate almost unchanged. The transfer data suggest that the neutron and γ strengths of the 830 keV resonance are about equal; direct measurements, most recently with a stilbene detector (Shahina et al. 2024), find the (α,n) strength about three times the (α,γ) strength.\n\nA direct measurement below the 830 keV resonance is the aim of the SHADES project, with a hybrid array of EJ-309 scintillators and ³He counters and a recirculating gas target at the MV machine of the Bellotti Ion Beam Facility (BIBF); the expected sensitivity gain is more than two orders of magnitude (Rapagnani et al. 2022).", "status": "uncertain", "statusNote": "Below the 830 keV resonance (E_α,lab; E_cm ≈ 702 keV) only upper limits exist from direct experiments, and the indirect constraints on the near-threshold ²⁶Mg states do not yet agree. A new direct measurement is under way at LUNA within the SHADES project.", "statusPlain": "At the energies that matter in stars, direct experiments give only upper limits, and the indirect methods do not yet agree.", "keywords": [], "methods": [ "direct-surface", "neutron-beams", "anc", "direct-underground" ], "measurements": [ { "year": 1993, "facility": null, "lab": "", "method": "direct-surface", "energy": "", "note": "Direct measurement of both s-process neutron sources, ²²Ne(α,n)²⁵Mg and ¹³C(α,n)¹⁶O, with new rates for each.", "refs": [ "drotleff1993" ], "lowestKeV": null, "luna": false }, { "year": 2001, "facility": "stuttgart-dynamitron", "lab": "", "method": "direct-surface", "energy": "E(α,lab) = 0.57–1.47 MeV", "note": "Windowless gas target Rhinoceros and a new neutron detector with active shielding, up to 50% efficiency and 0.02 counts/s background; the resulting rate lies well below earlier compilations for some stellar temperatures below 0.3 GK.", "refs": [ "jaeger2001" ], "lowestKeV": null, "luna": false }, { "year": 2017, "facility": "n-tof", "lab": "", "method": "neutron-beams", "energy": "²⁵Mg + n, thermal to about 300 keV neutron energy", "note": "²⁵Mg(n,γ) and total cross sections fitted together in an R-matrix analysis gave unambiguous spin-parity assignments for ²⁶Mg states above the neutron threshold; the limits point to a larger (α,n)/(α,γ) ratio than previously evaluated.", "refs": [ "massimi2017" ], "lowestKeV": null, "luna": false }, { "year": 2020, "facility": "texas-am", "lab": "", "method": "anc", "energy": "²²Ne(⁶Li,d)²⁶Mg in inverse kinematics", "note": "Deuterons and ²⁶Mg recoils detected in coincidence with the TIARA array and the MDM spectrometer; a new neutron/γ decay branching ratio for a key resonance gives it a new α strength.", "refs": [ "ota2020" ], "lowestKeV": null, "luna": false }, { "year": 2020, "facility": "texas-am", "lab": "", "method": "anc", "energy": "²²Ne(⁶Li,d) and ²²Ne(⁷Li,t), 1.0 MeV/u ²²Ne beam", "note": "Partial α widths of ²⁶Mg resonances in the Gamow window; the derived (α,n) and (α,γ) rates differ significantly from earlier values.", "refs": [ "jayatissa2020" ], "lowestKeV": null, "luna": false }, { "year": 2024, "facility": "notre-dame", "lab": "", "method": "direct-surface", "energy": "830 keV resonance (E_α,lab; E_cm ≈ 702 keV)", "note": "Strength of the key resonance remeasured with a stilbene detector; similar to the earlier direct results and about three times the (α,γ) strength, against transfer data that imply the two are about equal.", "refs": [ "shahina2024" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "angulo1999", "adsley2021" ], "rmatrix": [], "openQuestions": [ "A direct measurement below the 830 keV resonance, which needs the low neutron background of an underground laboratory and a neutron detector with energy sensitivity.", "Spin, parity and α width of the ²⁶Mg states just above the neutron threshold, where transfer and neutron-resonance data still disagree.", "The ratio of the (α,n) and (α,γ) strengths of the 830 keV resonance, about 3 in direct measurements and about 1 from transfer data." ], "facts": [], "related": [ "22Ne-ag-26Mg", "13C-an-16O", "18O-ag-22Ne", "14N-ag-18F", "25Mg-ng-26Mg" ], "q": { "value": -0.47833822999999853, "annihilation": false, "kinetic": -0.47833822999999853 }, "gamow": [ { "network": "neutron-sources", "label": "AGB thermal pulse", "T9": 0.27, "E0": 563.8926144860224, "width": 231.44120776104177, "lo": 478.33822999999853, "hi": 709.7794377610403, "threshold": 478.33822999999853, "thresholdLimited": true }, { "network": "neutron-sources", "label": "massive star, He core end", "T9": 0.3, "E0": 604.9248148264104, "width": 286.1272250957613, "lo": 478.33822999999853, "hi": 764.4654550957598, "threshold": 478.33822999999853, "thresholdLimited": true } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "drotleff1993", "jaeger2001", "massimi2017", "ota2020", "jayatissa2020", "shahina2024", "angulo1999", "adsley2021" ], "luna": false, "lunaYears": [] }, { "id": "22Ne-ag-26Mg", "hasFile": true, "label": "²²Ne(α,γ)²⁶Mg", "updated": null, "kind": "capture", "target": "22Ne", "projectile": "4He", "ejectile": "g", "product": "26Mg", "from": { "code": "22Ne", "A": 22, "Z": 10, "N": 12 }, "to": { "code": "26Mg", "A": 26, "Z": 12, "N": 14 }, "networks": [ "neutron-sources" ], "families": [ "neutrons" ], "importance": "major", "summary": "Neon-22 captures a helium nucleus and keeps it, becoming magnesium-26. It competes with the neutron-releasing reaction on the same nucleus.", "role": "Every neon-22 nucleus that captures helium through this reaction is lost as a neutron source. At lower temperatures this capture is faster than the neutron-producing reaction, so it decides how much neon-22 is still left when the star becomes hot enough to release neutrons. It also adds magnesium-26 to the gas the star returns to the Galaxy.", "details": "The rate is dominated by low-energy resonances in ²⁶Mg, chiefly those at E(α,lab) = 650 and 830 keV. For the 830 keV resonance Hunt et al. (2019) found ωγ = (4.6 ± 1.2)×10⁻⁵ eV at LENA, and Shahina et al. (2022) measured ωγ = 35 ± 4 µeV and give a weighted average with earlier measurements of 35 ± 2 µeV; for the 650 keV resonance they report an upper limit, ωγ < 0.15 µeV. At lower energies the resonance strengths come only from indirect data, and the literature values for the resonance at E = 334 keV (E(α,lab) ≈ 395 keV, Ex = 10949 keV) span a wide range. LUNA set the first direct upper limit on it, ωγ < 4.0×10⁻¹¹ eV at 90% confidence, with a windowless enriched ²²Ne gas target and a 4π BGO summing detector at the 400 kV accelerator; the background in the region of interest was below 0.5 counts per day (Piatti et al. 2022). The authors propose to extend the approach to higher energies at the 3.5 MV machine of the Bellotti Ion Beam Facility (BIBF).", "status": "uncertain", "statusNote": "The 830 keV resonance is measured to about 6%, but the lower-lying resonances are known only from indirect data and direct upper limits.", "statusPlain": "", "keywords": [], "methods": [ "direct-surface", "direct-underground", "anc" ], "measurements": [ { "year": 2019, "facility": "tunl-lena", "lab": "", "method": "direct-surface", "energy": "E(α,lab) = 0.83 MeV resonance", "note": "Implanted ²²Ne target and γγ-coincidence detection; E(α,lab) = 835.2 ± 3.0 keV and ωγ = (4.6 ± 1.2)×10⁻⁵ eV, higher than earlier values but overlapping within the uncertainties.", "refs": [ "hunt2019" ], "lowestKeV": null, "luna": false }, { "year": 2020, "facility": "texas-am", "lab": "", "method": "anc", "energy": "²²Ne(⁶Li,d) and ²²Ne(⁷Li,t), 1.0 MeV/u ²²Ne beam", "note": "Partial α widths of ²⁶Mg resonances in the Gamow window; the (α,γ) rate differs significantly from earlier values.", "refs": [ "jayatissa2020" ], "lowestKeV": null, "luna": false }, { "year": 2022, "facility": "luna-400", "lab": "", "method": "direct-underground", "energy": "E = 334 keV resonance", "note": "First direct limit, ωγ < 4.0×10⁻¹¹ eV (90% CL), higher than most indirect limits but free of their model assumptions.", "refs": [ "piatti2022" ], "lowestKeV": null, "luna": true }, { "year": 2022, "facility": "notre-dame", "lab": "", "method": "direct-surface", "energy": "E(α,lab) = 650 and 830 keV resonances", "note": "Implanted ²²Ne targets; ωγ(830 keV) = 35 ± 4 µeV and the first direct upper limit for the 650 keV resonance.", "refs": [ "shahina2022" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "angulo1999", "adsley2021" ], "rmatrix": [], "openQuestions": [ "The strengths of the resonances below 830 keV, in particular at E = 334 keV, where direct sensitivity must improve by orders of magnitude to reach the indirect estimates.", "Spin-parity assignments of the ²⁶Mg states in the Gamow window, which decide whether a state can be populated in α capture." ], "facts": [], "related": [ "22Ne-an-25Mg", "18O-ag-22Ne" ], "q": { "value": 10.61474387, "annihilation": false, "kinetic": 10.61474387 }, "gamow": [ { "network": "neutron-sources", "label": "AGB thermal pulse", "T9": 0.27, "E0": 563.8926144860224, "width": 264.5342248412417 }, { "network": "neutron-sources", "label": "massive star, He core end", "T9": 0.3, "E0": 604.9248148264104, "width": 288.81058763344583 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "hunt2019", "jayatissa2020", "piatti2022", "shahina2022", "angulo1999", "adsley2021" ], "luna": true, "lunaYears": [ 2022 ] }, { "id": "17O-an-20Ne", "hasFile": true, "label": "¹⁷O(α,n)²⁰Ne", "updated": null, "kind": "transfer", "target": "17O", "projectile": "4He", "ejectile": "n", "product": "20Ne", "from": { "code": "17O", "A": 17, "Z": 8, "N": 9 }, "to": { "code": "20Ne", "A": 20, "Z": 10, "N": 10 }, "networks": [ "neutron-sources" ], "families": [ "neutrons" ], "importance": "minor", "summary": "Oxygen-17 captures a helium nucleus and gives back a neutron. It decides whether neutrons swallowed by the abundant oxygen-16 are lost or returned.", "role": "In massive stars, and even more in stars poor in heavy elements, oxygen-16 is very abundant and captures many of the neutrons released by neon-22. These neutrons would be lost to the s-process, which is why oxygen-16 is called a neutron poison. The oxygen-17 it forms can capture a helium nucleus in two ways. This reaction releases the neutron again, while the competing ¹⁷O(α,γ)²¹Ne keeps it. The ratio of the two decides how strongly oxygen-16 poisons the s-process, and therefore how many heavy elements metal-poor massive stars can make.", "details": "The relevant quantity is the ratio of the (α,n) and (α,γ) rates at T₉ ≈ 0.2–0.3, set by resonances in ²¹Ne above the α threshold. Best et al. (2013) measured the (α,n) channel at Notre Dame between E(α,lab) = 0.8 and 2.3 MeV with a moderating neutron detector, and independently through the 1633 keV γ-ray of ²⁰Ne; a simultaneous R-matrix fit to both channels gave a new rate for 0.1–10 GK. They found the (α,γ) channel strong enough to compete with the neutron channel, so neutrons are recycled less efficiently than assumed when the (α,γ) channel was taken to be very weak. In the competing channel, DRAGON measurements in inverse kinematics set an upper limit of 140 neV (95% CL) on the 612 keV resonance, which removes it from the (α,γ) rate (Williams et al. 2022).", "status": "uncertain", "statusNote": "What matters is the (α,n)/(α,γ) ratio; both channels have been measured directly, but not at the lowest energies of core helium burning.", "statusPlain": "What matters is how this reaction competes with ¹⁷O(α,γ)²¹Ne; both have been measured, but not at the lowest energies of helium burning.", "keywords": [], "methods": [ "direct-surface", "inverse-kinematics" ], "measurements": [ { "year": 2013, "facility": "notre-dame", "lab": "", "method": "direct-surface", "energy": "E(α,lab) = 0.8–2.3 MeV", "note": "(α,n) cross section with a moderating neutron detector and, separately, from the 1633 keV γ-ray of ²⁰Ne; R-matrix fit to both channels and a new rate for 0.1–10 GK.", "refs": [ "best2013" ], "lowestKeV": null, "luna": false }, { "year": 2022, "facility": "dragon", "lab": "", "method": "inverse-kinematics", "energy": "¹⁷O(α,γ)²¹Ne resonances between 612 and 1318 keV", "note": "Competing (α,γ) channel: upper limit ωγ < 140 neV (95% CL) for the 612 keV resonance; the new (α,γ) rate is lower than earlier ones and increases the weak s-process yields of a rotating low-metallicity 20 M☉ star.", "refs": [ "williams2022" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "angulo1999" ], "rmatrix": [], "openQuestions": [ "The ratio of ¹⁷O(α,n)²⁰Ne to ¹⁷O(α,γ)²¹Ne at the temperatures of core helium burning and shell carbon burning." ], "facts": [], "related": [ "22Ne-an-25Mg", "13C-an-16O", "17O-pa-14N" ], "q": { "value": 0.5867657699999995, "annihilation": false, "kinetic": 0.5867657699999995 }, "gamow": [ { "network": "neutron-sources", "label": "massive star, He core end", "T9": 0.3, "E0": 513.6792531560187, "width": 266.13894000708257 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "best2013", "williams2022", "angulo1999" ], "luna": false, "lunaYears": [] }, { "id": "14N-np-14C", "hasFile": true, "label": "¹⁴N(n,p)¹⁴C", "updated": null, "kind": "transfer", "target": "14N", "projectile": "n", "ejectile": "1H", "product": "14C", "from": { "code": "14N", "A": 14, "Z": 7, "N": 7 }, "to": { "code": "14C", "A": 14, "Z": 6, "N": 8 }, "networks": [ "neutron-poisons" ], "families": [ "neutrons" ], "importance": "major", "summary": "Nitrogen-14 absorbs a neutron and releases a proton, becoming carbon-14. It is the most dangerous neutron poison in the ¹³C pocket of giant stars.", "role": "In an AGB star the neutrons that build the heavy elements come from a thin layer rich in carbon-13, the ¹³C pocket. Wherever that layer also holds nitrogen-14, the nitrogen captures neutrons readily and turns them into protons, so they never reach the iron seeds. How large this loss is decides how many neutrons each iron nucleus receives, and so how far the s-process climbs towards lead. The reaction is also used in medicine and dosimetry, which is one reason it has been measured often.", "details": "The first resonances of ¹⁴N(n,p)¹⁴C lie at 492.7 and 644 keV. Its competition with ¹³C(α,n)¹⁶O for the neutrons of the pocket is why stellar models require the ¹³C pocket to form where little ¹⁴N is present (Straniero et al. 2006). Activation at Karlsruhe with a quasi-Maxwellian spectrum of kT = 25 keV and at 123–182 keV, with the ¹⁴C counted by accelerator mass spectrometry at VERA, gave cross sections about two times lower between 100 and 200 keV than earlier experiments and evaluations (Wallner et al. 2016). A time-of-flight measurement at n_TOF EAR2 from subthermal energy to 800 keV, relative to ¹⁰B(n,α) and ²³⁵U(n,f), gave a thermal cross section of 1.809 ± 0.045 b and a 492.7 keV resonance whose low-energy tail lies below the evaluations, and Maxwellian-averaged cross sections from it (Torres-Sánchez et al. 2023).\n\nThe protons it releases are not simply lost. Captured by ¹²C they make ¹³C again, through ¹²C(p,γ)¹³N(β⁺)¹³C, and so a little of the neutron source; captured by ¹⁸O they open the chain ¹⁸O(p,α)¹⁵N(α,γ)¹⁹F, by which AGB stars make fluorine.", "status": "improving", "statusNote": "Recent activation and time-of-flight data disagree with older ones in the keV region; the n_TOF data cover the whole range from thermal to 800 keV with 2.5% accuracy.", "statusPlain": "Well measured at low energies; at the energies inside stars, recent experiments are correcting older values.", "keywords": [], "methods": [ "activation", "neutron-beams" ], "measurements": [ { "year": 2016, "facility": "karlsruhe-vdg", "lab": "", "method": "activation", "energy": "quasi-Maxwellian kT = 25 keV; 123–182 keV", "note": "Irradiations at Karlsruhe, ¹⁴C counted by AMS at VERA (Vienna); about two times lower cross sections between 100 and 200 keV than previous experiments and evaluations.", "refs": [ "wallner2016" ], "lowestKeV": null, "luna": false }, { "year": 2023, "facility": "n-tof", "lab": "", "method": "neutron-beams", "energy": "subthermal to 800 keV (neutron energy)", "note": "EAR2 measurement relative to ¹⁰B(n,α)⁷Li and ²³⁵U(n,f); thermal cross section 1.809 ± 0.045 b, consistent with ENDF/B-VIII.0 and JEFF-3.3; first two resonances resolved; MACS derived.", "refs": [ "torressanchez2023" ], "lowestKeV": null, "luna": false }, { "year": 2025, "facility": "hzdr", "lab": "", "method": "neutron-beams", "energy": "0.1–12 MeV (neutron energy), total cross section", "note": "Transmission measurement at the nELBE time-of-flight facility, only the second high-sensitivity total cross section of ¹⁴N + n, as a constraint for R-matrix evaluations of the (n,p) channel. Good agreement with earlier data except at the lowest resonance, E_n = 433 keV.", "refs": [ "deboer2025" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "bao2000", "dillmann2014", "dillmann2008" ], "rmatrix": [], "openQuestions": [ "The cross section between about 10 and 100 keV, where the measurements of different groups still differ." ], "facts": [ { "text": "The same reaction that steals neutrons in giant stars also matters on Earth: knowing it well helps to estimate the yields of the nuclear weapons tested in the atmosphere.", "refs": [ "deboer2025" ] } ], "related": [ "13C-an-16O", "22Ne-ng-23Ne", "16O-ng-17O" ], "q": { "value": 0.6258708359999989, "annihilation": false, "kinetic": 0.6258708359999989 }, "gamow": [], "thermal": [ { "network": "neutron-poisons", "label": "AGB ¹³C pocket", "T9": 0.09, "kT": 7.7555997 } ], "windowNote": "A neutron feels no Coulomb barrier, so there is no Gamow window: the relevant energies are those of the thermal distribution itself, around kT.", "halfLife": null, "productHalfLife": { "seconds": 179874478200, "stable": false, "text": "5 700 yr" }, "references": [ "wallner2016", "torressanchez2023", "deboer2025", "bao2000", "dillmann2014", "dillmann2008" ], "luna": false, "lunaYears": [] }, { "id": "22Ne-ng-23Ne", "hasFile": true, "label": "²²Ne(n,γ)²³Ne", "updated": null, "kind": "capture", "target": "22Ne", "projectile": "n", "ejectile": "g", "product": "23Ne", "from": { "code": "22Ne", "A": 22, "Z": 10, "N": 12 }, "to": { "code": "23Ne", "A": 23, "Z": 10, "N": 13 }, "networks": [ "neutron-poisons" ], "families": [ "neutrons" ], "importance": "minor", "summary": "Neon-22, the fuel of the neutron source in massive stars, also captures some of the neutrons that it releases.", "role": "In massive stars nearly all neutrons come from ²²Ne(α,n)²⁵Mg. Neon-22 is far more abundant than iron, so even though a single neon nucleus is very unlikely to capture a neutron, together they take a noticeable share. Each neutron captured by neon is lost to the heavy elements. The product, neon-23, decays within a minute to sodium-23.", "details": "The Maxwellian-averaged cross section of ²²Ne is tiny, but its abundance in helium-burning matter makes it a significant poison. It was measured by activation together with other noble-gas isotopes in the keV region (Beer et al. 2002) and with the prompt capture γ-rays at the Tokyo Institute of Technology, where the discrete γ-rays from the capture states were observed for the first time and the direct p-wave capture was identified (Tomyo et al. 2003). Heil et al. (2014) re-analysed the keV resonance data of the three stable neon isotopes with the R-matrix code SAMMY, adding direct-capture components, and gave new Maxwellian-averaged cross sections; they found that earlier work had grossly overestimated the stellar rates of ²⁰Ne and ²¹Ne (an erratum appeared in 2015).", "status": "improving", "statusNote": "The 2014 R-matrix reanalysis changed the stellar rates of the neon isotopes substantially compared with earlier compilations.", "statusPlain": "Measured, but a 2014 reanalysis changed the values for the neon isotopes substantially from the older compilations.", "keywords": [], "methods": [ "activation", "neutron-beams" ], "measurements": [ { "year": 2002, "facility": null, "lab": "", "method": "activation", "energy": "keV region", "note": "Capture on ²²Ne measured together with ⁴⁰Ar and the krypton isotopes ⁷⁸,⁸⁰,⁸⁴,⁸⁶Kr.", "refs": [ "beer2002" ], "lowestKeV": null, "luna": false }, { "year": 2003, "facility": null, "lab": "Tokyo Institute of Technology, 3.2 MV Pelletron", "method": "neutron-beams", "energy": "keV neutrons, prompt capture γ-rays", "note": "Discrete γ-rays from the capture states of ²⁰Ne and ²²Ne observed for the first time; non-resonant direct p-wave capture identified; MACS larger than earlier values.", "refs": [ "tomyo2003" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "heil2014", "bao2000", "dillmann2008" ], "rmatrix": [], "openQuestions": [], "facts": [], "related": [ "22Ne-an-25Mg", "14N-np-14C", "16O-ng-17O" ], "q": { "value": 5.200652099999999, "annihilation": false, "kinetic": 5.200652099999999 }, "gamow": [], "thermal": [ { "network": "neutron-poisons", "label": "massive star, core helium burning", "T9": 0.3, "kT": 25.851999 } ], "windowNote": "A neutron feels no Coulomb barrier, so there is no Gamow window: the relevant energies are those of the thermal distribution itself, around kT.", "halfLife": null, "productHalfLife": { "seconds": 37.15, "stable": false, "text": "37.1 s" }, "references": [ "beer2002", "tomyo2003", "heil2014", "bao2000", "dillmann2008" ], "luna": false, "lunaYears": [] }, { "id": "16O-ng-17O", "hasFile": true, "label": "¹⁶O(n,γ)¹⁷O", "updated": null, "kind": "capture", "target": "16O", "projectile": "n", "ejectile": "g", "product": "17O", "from": { "code": "16O", "A": 16, "Z": 8, "N": 8 }, "to": { "code": "17O", "A": 17, "Z": 8, "N": 9 }, "networks": [ "neutron-poisons" ], "families": [ "neutrons" ], "importance": "major", "summary": "Oxygen-16 captures a neutron. Oxygen is so abundant that this tiny cross section makes it one of the main neutron poisons in massive stars.", "role": "In the helium core and the carbon-burning shells of a massive star, oxygen-16 is among the most abundant nuclei. Every neutron it captures is taken from the iron seeds of the weak s-process. The loss is not always final: the oxygen-17 it makes can capture a helium nucleus and give the neutron back through ¹⁷O(α,n)²⁰Ne, so the two reactions together decide how strongly oxygen poisons the process.", "details": "At stellar energies the cross section is dominated by non-resonant direct p-wave capture, which makes it rise with energy rather than fall as 1/v; this was established by measurements between 10 and 80 keV (Igashira et al. 1995). Mohr et al. (2016) re-evaluated all data and recommended Maxwellian-averaged cross sections from kT = 5 to 100 keV that are lower than the previous recommendation up to kT = 60 keV and up to 14% higher at 100 keV, and studied the effect on the weak s-process in core helium burning (kT = 26 keV) and shell carbon burning (kT = 90 keV).", "status": "improving", "statusNote": "The 2016 re-evaluation of all data changed the energy dependence of the recommended stellar cross section.", "statusPlain": "Measured, but small and hard to measure; a 2016 review of all the data changed how the recommended value varies with temperature.", "keywords": [], "methods": [ "neutron-beams" ], "measurements": [ { "year": 1995, "facility": null, "lab": "", "method": "neutron-beams", "energy": "10–80 keV (neutron energy)", "note": "Cross section measured at stellar energies; it is dominated by nonresonant direct p-wave capture, and the Maxwellian average was derived.", "refs": [ "igashira1995" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "bao2000", "mohr2016" ], "rmatrix": [], "openQuestions": [], "facts": [], "related": [ "17O-an-20Ne", "22Ne-ng-23Ne", "14N-np-14C" ], "q": { "value": 4.143080199999999, "annihilation": false, "kinetic": 4.143080199999999 }, "gamow": [], "thermal": [ { "network": "neutron-poisons", "label": "massive star, core helium burning", "T9": 0.3, "kT": 25.851999 } ], "windowNote": "A neutron feels no Coulomb barrier, so there is no Gamow window: the relevant energies are those of the thermal distribution itself, around kT.", "halfLife": null, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "igashira1995", "bao2000", "mohr2016" ], "luna": false, "lunaYears": [] }, { "id": "25Mg-ng-26Mg", "hasFile": true, "label": "²⁵Mg(n,γ)²⁶Mg", "updated": null, "kind": "capture", "target": "25Mg", "projectile": "n", "ejectile": "g", "product": "26Mg", "from": { "code": "25Mg", "A": 25, "Z": 12, "N": 13 }, "to": { "code": "26Mg", "A": 26, "Z": 12, "N": 14 }, "networks": [ "neutron-poisons" ], "families": [ "neutrons" ], "importance": "major", "summary": "Magnesium-25 captures a neutron. In massive stars it is the strongest neutron poison, and the neutron source makes it itself.", "role": "In a massive star almost every neutron comes from ²²Ne(α,n)²⁵Mg, so each neutron released leaves behind a magnesium-25 nucleus. Magnesium-25 then competes with the iron seeds for the next neutrons: in stars with about the Sun's composition it is the most important poison of the weak s-process. How readily it captures decides how many neutrons are left for the iron, and so how much copper, gallium, germanium and the other weak-component nuclei the star makes.", "details": "The stellar cross section is dominated by a few s- and p-wave resonances in the keV region. At n_TOF the capture yields of the three stable magnesium isotopes were measured with C₆D₆ detectors and analysed together with transmission data on natural magnesium; the Maxwellian-averaged cross section of ²⁵Mg at kT = 30 keV is 4.1 ± 0.6 mb (Massimi et al. 2012). New capture data from n_TOF and transmission data from GELINA on enriched ²⁵Mg then fixed the spins and parities of the ²⁶Mg states above the neutron threshold, the same states that the neutron source ²²Ne(α,n)²⁵Mg populates (Massimi et al. 2017).", "status": "improving", "statusNote": "Resonance parameters from n_TOF capture and GELINA transmission data give the stellar cross section to about 15% at kT = 30 keV.", "statusPlain": "Measured with neutron beams at CERN and Geel; known to about 15%.", "keywords": [], "methods": [ "neutron-beams" ], "measurements": [ { "year": 2012, "facility": "n-tof", "lab": "", "method": "neutron-beams", "energy": "resolved resonances (neutron energy)", "note": "Capture on ²⁴,²⁵,²⁶Mg with C₆D₆ detectors, shape analysis together with transmission data; MACS at 30 keV 4.1 ± 0.6 mb for ²⁵Mg.", "refs": [ "massimi2012" ], "lowestKeV": null, "luna": false }, { "year": 2017, "facility": "n-tof", "lab": "", "method": "neutron-beams", "energy": "resolved resonances, with transmission at GELINA", "note": "Capture at n_TOF and transmission at GELINA on enriched ²⁵Mg: spins and parities of the ²⁶Mg states above the neutron threshold.", "refs": [ "massimi2017" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "bao2000", "dillmann2014" ], "rmatrix": [], "openQuestions": [], "facts": [], "related": [ "22Ne-an-25Mg", "22Ne-ng-23Ne", "16O-ng-17O" ], "q": { "value": 11.093082099999998, "annihilation": false, "kinetic": 11.093082099999998 }, "gamow": [], "thermal": [ { "network": "neutron-poisons", "label": "massive star, core helium burning", "T9": 0.3, "kT": 25.851999 } ], "windowNote": "A neutron feels no Coulomb barrier, so there is no Gamow window: the relevant energies are those of the thermal distribution itself, around kT.", "halfLife": null, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "massimi2012", "massimi2017", "bao2000", "dillmann2014" ], "luna": false, "lunaYears": [] }, { "id": "56Fe-ng-57Fe", "hasFile": true, "label": "⁵⁶Fe(n,γ)⁵⁷Fe", "updated": null, "kind": "capture", "target": "56Fe", "projectile": "n", "ejectile": "g", "product": "57Fe", "from": { "code": "56Fe", "A": 56, "Z": 26, "N": 30 }, "to": { "code": "57Fe", "A": 57, "Z": 26, "N": 31 }, "networks": [ "s-main", "s-weak" ], "families": [ "s-process" ], "importance": "key", "summary": "Iron-56 captures a neutron. It is the first step of the s-process: almost every heavy nucleus the process makes began as an iron seed.", "role": "Of all the nuclei heavier than those that stars burn for energy, iron-56 is by far the most abundant, and it was already present in the gas the star formed from. Neutrons released inside the star are captured one by one, first by iron and then by its heavier products, which climb step by step towards lead. How readily iron captures a neutron sets how many seeds are put on the path; together with the number of neutrons available per seed, it decides how far the s-process goes.", "details": "The stellar rate is given as a Maxwellian-averaged cross section (MACS); the reference compilation of Bao et al. (2000) recommends values at kT = 30 keV, scaled to kT = 5–100 keV, and its successor KADoNiS (Dillmann et al. 2008) updates them. The cross section of the iron isotopes in the keV region is dominated by resolved resonances measured by time of flight. Wang et al. (2014) measured keV-neutron capture on ⁵⁶Fe and ⁵⁷Fe by time of flight with a ⁷Li(p,n)⁷Be neutron source and derived the MACS of both isotopes. The product ⁵⁷Fe is stable, as is ⁵⁸Fe; the chain first meets a radioactive nucleus at ⁵⁹Fe.", "status": "improving", "statusNote": "The recommended stellar cross section rests on time-of-flight resonance data collected over several decades and compiled by Bao et al. and KADoNiS; newer measurements refine it.", "statusPlain": "Measured many times over several decades with neutron beams; newer measurements still refine it.", "keywords": [ "iron", "seed", "Fe-56" ], "methods": [ "neutron-beams", "activation" ], "measurements": [ { "year": 2014, "facility": null, "lab": "", "method": "neutron-beams", "energy": "keV neutrons from ⁷Li(p,n)⁷Be", "note": "Capture cross sections of ⁵⁶Fe and ⁵⁷Fe by time of flight; Maxwellian-averaged cross sections derived for both isotopes.", "refs": [ "wang2014" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "bao2000", "dillmann2008" ], "rmatrix": [], "openQuestions": [], "facts": [], "related": [ "62Ni-ng-63Ni", "22Ne-an-25Mg", "13C-an-16O", "197Au-ng-198Au" ], "q": { "value": 7.6461781, "annihilation": false, "kinetic": 7.6461781 }, "gamow": [], "thermal": [ { "network": "s-main", "label": "AGB ¹³C pocket", "T9": 0.09, "kT": 7.7555997 }, { "network": "s-main", "label": "AGB thermal pulse", "T9": 0.27, "kT": 23.266799100000004 }, { "network": "s-weak", "label": "massive star, core helium burning", "T9": 0.3, "kT": 25.851999 }, { "network": "s-weak", "label": "massive star, shell carbon burning", "T9": 1.04, "kT": 89.62026320000001 } ], "windowNote": "A neutron feels no Coulomb barrier, so there is no Gamow window: the relevant energies are those of the thermal distribution itself, around kT.", "halfLife": null, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "wang2014", "bao2000", "dillmann2008" ], "luna": false, "lunaYears": [] }, { "id": "85Kr-ng-86Kr", "hasFile": true, "label": "⁸⁵Kr(n,γ)⁸⁶Kr", "updated": null, "kind": "capture", "target": "85Kr", "projectile": "n", "ejectile": "g", "product": "86Kr", "from": { "code": "85Kr", "A": 85, "Z": 36, "N": 49 }, "to": { "code": "86Kr", "A": 86, "Z": 36, "N": 50 }, "networks": [ "s-main", "s-weak" ], "families": [ "s-process" ], "importance": "key", "summary": "Radioactive krypton-85 captures a neutron. Whether it does so or decays first tells how dense the neutrons were in the star, and it has never been measured directly.", "role": "Krypton-85 lives about ten years in the laboratory. In the ¹³C pocket of an AGB star a nucleus waits a few centuries for its next neutron, and in the brief ²²Ne bursts only a few months, so whether krypton-85 decays or captures depends on where it is made. If neutrons are few, it decays into rubidium-85; if they are many, it captures another one and becomes krypton-86, and the flow then reaches rubidium-87 through the next capture. The amounts of krypton-86 and of the two rubidium isotopes therefore record the neutron density, and so tell the two neutron sources apart. Krypton-86 in stardust grains from AGB stars, found in meteorites, is one of the clues read in this way.", "details": "⁸⁵Kr sits at the branching that feeds the s-process side of the N = 50 closed shell, where ⁸⁶Kr, ⁸⁷Rb and ⁸⁸Sr have magic neutron number; the branching is a classic neutron-density indicator (Käppeler et al. 2011). Not all the flow reaches the 10.7 yr ground state: about 40–60% of the captures on ⁸⁴Kr make ⁸⁵Kr in its 4.5 h isomeric state, and about 80% of those decay straight to ⁸⁵Rb, bypassing the branching (Lugaro and Chieffi 2011). There is no direct measurement, and the stellar cross section comes from statistical-model calculations. Raut et al. (2013) constrained it indirectly: they measured the photodisintegration ⁸⁶Kr(γ,n) at HIγS with monoenergetic photons from the neutron separation energy (9.86 MeV) to 13 MeV, combined it with ⁸⁶Kr(γ,γ′) data into the dipole response of ⁸⁶Kr, and used it to predict the ⁸⁵Kr(n,γ) cross section. With it, AGB models of less than about 1.5 M☉, in which the ¹³C burns convectively, are a possible explanation for the highest ⁸⁶Kr/⁸²Kr ratios of presolar SiC grains.", "status": "unmeasured", "statusNote": "No direct measurement exists; the stellar cross section comes from statistical-model calculations constrained by ⁸⁶Kr photodisintegration.", "statusPlain": "Never measured directly: the rate of this radioactive gas is inferred from calculations and indirect experiments.", "keywords": [ "krypton-85", "Kr-85", "branch point", "stardust" ], "methods": [ "photonuclear", "theory" ], "measurements": [ { "year": 2013, "facility": null, "lab": "HIγS, Triangle Universities Nuclear Laboratory", "method": "photonuclear", "energy": "⁸⁶Kr(γ,n), photons from 9.86 to 13 MeV", "note": "Photodisintegration of ⁸⁶Kr with monoenergetic photons; with ⁸⁶Kr(γ,γ′) it fixes the dipole strength used to predict ⁸⁵Kr(n,γ).", "refs": [ "raut2013" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "bao2000", "dillmann2008", "kaeppeler2011", "lugaro2011" ], "rmatrix": [], "openQuestions": [ "A direct measurement of the capture cross section on a ⁸⁵Kr sample." ], "facts": [], "related": [ "63Ni-ng-64Ni", "151Sm-ng-152Sm", "22Ne-an-25Mg", "13C-an-16O" ], "q": { "value": 9.856694099999999, "annihilation": false, "kinetic": 9.856694099999999 }, "gamow": [], "thermal": [ { "network": "s-main", "label": "AGB ¹³C pocket", "T9": 0.09, "kT": 7.7555997 }, { "network": "s-main", "label": "AGB thermal pulse", "T9": 0.27, "kT": 23.266799100000004 }, { "network": "s-weak", "label": "massive star, core helium burning", "T9": 0.3, "kT": 25.851999 }, { "network": "s-weak", "label": "massive star, shell carbon burning", "T9": 1.04, "kT": 89.62026320000001 } ], "windowNote": "A neutron feels no Coulomb barrier, so there is no Gamow window: the relevant energies are those of the thermal distribution itself, around kT.", "halfLife": { "seconds": 338542702.128, "stable": false, "text": "10.7 yr" }, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "raut2013", "bao2000", "dillmann2008", "kaeppeler2011", "lugaro2011" ], "luna": false, "lunaYears": [] }, { "id": "93Zr-ng-94Zr", "hasFile": true, "label": "⁹³Zr(n,γ)⁹⁴Zr", "updated": null, "kind": "capture", "target": "93Zr", "projectile": "n", "ejectile": "g", "product": "94Zr", "from": { "code": "93Zr", "A": 93, "Z": 40, "N": 53 }, "to": { "code": "94Zr", "A": 94, "Z": 40, "N": 54 }, "networks": [ "s-main" ], "families": [ "s-process" ], "importance": "major", "summary": "Radioactive zirconium-93 captures a neutron. It lives so long that in a star it behaves almost like a stable nucleus; what is left of it decays later into niobium.", "role": "Zirconium-93 lives about 1.6 million years, far longer than the wait between two neutron captures, so in an AGB star it captures neutrons and the path continues to zirconium-94. The zirconium-93 still left when the star throws off its envelope decays afterwards into niobium-93, the only stable isotope of niobium. Its capture rate therefore matters both for the zirconium isotopes and for the niobium the s-process makes.", "details": "The capture on the radioactive ⁹³Zr was measured at n_TOF and analysed in resolved resonances up to 8 keV neutron energy; the capture widths came out about 14% smaller than in an earlier experiment (Tagliente et al. 2013). Above 8 keV the stellar cross section still rests on evaluations, so the MACS at kT = 30 keV is only partly measured.", "status": "uncertain", "statusNote": "Resonances measured at n_TOF up to 8 keV; the higher energies that matter at kT = 30 keV come from evaluations.", "statusPlain": "Measured at CERN at low energies only; at the higher energies of a star it still rests on estimates.", "keywords": [ "zirconium-93", "Zr-93", "niobium-93", "long-lived radioactive" ], "methods": [ "neutron-beams" ], "measurements": [ { "year": 2013, "facility": "n-tof", "lab": "", "method": "neutron-beams", "energy": "resolved resonances up to 8 keV (neutron energy)", "note": "Radioactive ⁹³Zr sample; capture widths about 14% smaller than in an earlier experiment.", "refs": [ "tagliente2013" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "bao2000", "dillmann2008" ], "rmatrix": [], "openQuestions": [], "facts": [], "related": [ "85Kr-ng-86Kr", "56Fe-ng-57Fe", "197Au-ng-198Au" ], "q": { "value": 8.218648099999996, "annihilation": false, "kinetic": 8.218648099999996 }, "gamow": [], "thermal": [ { "network": "s-main", "label": "AGB ¹³C pocket", "T9": 0.09, "kT": 7.7555997 }, { "network": "s-main", "label": "AGB thermal pulse", "T9": 0.27, "kT": 23.266799100000004 } ], "windowNote": "A neutron feels no Coulomb barrier, so there is no Gamow window: the relevant energies are those of the thermal distribution itself, around kT.", "halfLife": { "seconds": 50806650860000, "stable": false, "text": "1.61 million yr" }, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "tagliente2013", "bao2000", "dillmann2008" ], "luna": false, "lunaYears": [] }, { "id": "147Pm-ng-148Pm", "hasFile": true, "label": "¹⁴⁷Pm(n,γ)¹⁴⁸Pm", "updated": null, "kind": "capture", "target": "147Pm", "projectile": "n", "ejectile": "g", "product": "148Pm", "from": { "code": "147Pm", "A": 147, "Z": 61, "N": 86 }, "to": { "code": "148Pm", "A": 148, "Z": 61, "N": 87 }, "networks": [ "s-main" ], "families": [ "s-process" ], "importance": "major", "summary": "Radioactive promethium-147 captures a neutron. It is one of the branch points that decide how much of the s-process flow passes by samarium-148.", "role": "Promethium-147 lives about two and a half years in the laboratory. In an AGB star it either decays into samarium-147 or captures a neutron and moves on to promethium-148, which can capture again. Together with the branchings at neodymium-147 and promethium-148, the share decides how much of the flow skips samarium-148. Samarium-148 and samarium-150 are both made only by the s-process, and only the first is bypassed, so their ratio in the Solar System measures the neutron density in the stars that made them.", "details": "The stellar cross section was measured by activation at the Karlsruhe Van de Graaff with a quasi-Maxwellian spectrum. The 2.62 yr half-life limited the sample to 28 ng, about 10¹⁴ atoms. The partial cross sections to the 5.37 d ground state and to the 41.3 d isomer of ¹⁴⁸Pm were determined separately, giving a total of 709 ± 100 mb at kT = 30 keV; the cross sections of the other branch points, ¹⁴⁷Nd and ¹⁴⁸Pm, and the effect of thermally excited states came from statistical-model calculations (Reifarth et al. 2003). The branchings at ¹⁴⁷Nd, ¹⁴⁷Pm and ¹⁴⁸Pm set the ¹⁴⁸Sm/¹⁵⁰Sm ratio of the two s-only samarium isotopes (Käppeler et al. 2011).", "status": "uncertain", "statusNote": "One activation measurement, on a 28 ng sample, known to about 14%; the neighbouring branch points ¹⁴⁷Nd and ¹⁴⁸Pm rest on calculations.", "statusPlain": "Measured once, on a tiny radioactive sample, to about 14%; its neighbouring branch points are known only from calculations.", "keywords": [ "promethium-147", "Pm-147", "branch point", "samarium-148" ], "methods": [ "activation" ], "measurements": [ { "year": 2003, "facility": "karlsruhe-vdg", "lab": "", "method": "activation", "energy": "quasi-Maxwellian neutron spectrum", "note": "28 ng sample (about 10¹⁴ atoms); partial cross sections to the ground state and the 41.3 d isomer of ¹⁴⁸Pm; total 709 ± 100 mb at kT = 30 keV.", "refs": [ "reifarth2003" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "bao2000", "dillmann2008", "kaeppeler2011" ], "rmatrix": [], "openQuestions": [], "facts": [], "related": [ "151Sm-ng-152Sm", "171Tm-ng-172Tm", "85Kr-ng-86Kr" ], "q": { "value": 5.895318099999997, "annihilation": false, "kinetic": 5.895318099999997 }, "gamow": [], "thermal": [ { "network": "s-main", "label": "AGB ¹³C pocket", "T9": 0.09, "kT": 7.7555997 }, { "network": "s-main", "label": "AGB thermal pulse", "T9": 0.27, "kT": 23.266799100000004 } ], "windowNote": "A neutron feels no Coulomb barrier, so there is no Gamow window: the relevant energies are those of the thermal distribution itself, around kT.", "halfLife": { "seconds": 82786439.6684, "stable": false, "text": "2.62 yr" }, "productHalfLife": { "seconds": 463795.2, "stable": false, "text": "5.37 d" }, "references": [ "reifarth2003", "bao2000", "dillmann2008", "kaeppeler2011" ], "luna": false, "lunaYears": [] }, { "id": "151Sm-ng-152Sm", "hasFile": true, "label": "¹⁵¹Sm(n,γ)¹⁵²Sm", "updated": null, "kind": "capture", "target": "151Sm", "projectile": "n", "ejectile": "g", "product": "152Sm", "from": { "code": "151Sm", "A": 151, "Z": 62, "N": 89 }, "to": { "code": "152Sm", "A": 152, "Z": 62, "N": 90 }, "networks": [ "s-main" ], "families": [ "s-process" ], "importance": "key", "summary": "Radioactive samarium-151 captures a neutron. It is a classic branch point of the s-process, whose capture has been measured on a radioactive sample.", "role": "Samarium-151 lives about 95 years in the laboratory. In an AGB star it either captures a neutron, continuing the main path to samarium-152, or decays into europium-151, opening a side path through the europium isotopes. Its decay in a star depends on the temperature, so the share of the two paths depends both on the neutron density and on how hot the star is. Comparing the predicted and the observed abundances of the samarium, europium and gadolinium isotopes in the Solar System therefore tests the conditions inside the stars that made them.", "details": "At n_TOF the cross section was measured from 1 eV to 1 MeV on a radioactive ¹⁵¹Sm sample; the Maxwellian-averaged cross section at kT = 30 keV, 3100 ± 160 mb, is significantly larger than the theoretical predictions used before (Abbondanno et al. 2004). At Karlsruhe the stellar cross section was measured with the 4π BaF₂ detector and neutrons from the 3.7 MV Van de Graaff (Wisshak et al. 2006). The branchings at ¹⁴⁷Nd, ¹⁴⁷Pm, ¹⁴⁸Pm and ¹⁵¹Sm together determine the abundances of the s-only isotopes ¹⁴⁸Sm and ¹⁵⁰Sm, which are shielded from the r-process by ¹⁴⁸Nd and ¹⁵⁰Nd (Käppeler et al. 2011).", "status": "improving", "statusNote": "Measured at n_TOF and at Karlsruhe with radioactive samples; the temperature dependence of the stellar decay rate remains a separate input.", "statusPlain": "Measured on radioactive samples at CERN and Karlsruhe; how fast samarium-151 decays in a hot star is a separate question.", "keywords": [ "samarium-151", "Sm-151", "branch point" ], "methods": [ "neutron-beams" ], "measurements": [ { "year": 2004, "facility": "n-tof", "lab": "", "method": "neutron-beams", "energy": "1 eV – 1 MeV (neutron energy)", "note": "Radioactive sample; MACS at kT = 30 keV of 3100 ± 160 mb, well above the earlier theoretical estimates.", "refs": [ "abbondanno2004" ], "lowestKeV": null, "luna": false }, { "year": 2006, "facility": "karlsruhe-vdg", "lab": "", "method": "neutron-beams", "energy": "keV neutrons, 4π BaF₂ detector", "note": "Stellar capture cross section of the branch point measured with the Karlsruhe 4π barium fluoride array.", "refs": [ "wisshak2006" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "bao2000", "dillmann2008", "kaeppeler2011" ], "rmatrix": [], "openQuestions": [], "facts": [], "related": [ "85Kr-ng-86Kr", "197Au-ng-198Au", "63Ni-ng-64Ni" ], "q": { "value": 8.257818100000009, "annihilation": false, "kinetic": 8.257818100000009 }, "gamow": [], "thermal": [ { "network": "s-main", "label": "AGB ¹³C pocket", "T9": 0.09, "kT": 7.7555997 }, { "network": "s-main", "label": "AGB thermal pulse", "T9": 0.27, "kT": 23.266799100000004 } ], "windowNote": "A neutron feels no Coulomb barrier, so there is no Gamow window: the relevant energies are those of the thermal distribution itself, around kT.", "halfLife": { "seconds": 2985285199.6, "stable": false, "text": "94.6 yr" }, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "abbondanno2004", "wisshak2006", "bao2000", "dillmann2008", "kaeppeler2011" ], "luna": false, "lunaYears": [] }, { "id": "171Tm-ng-172Tm", "hasFile": true, "label": "¹⁷¹Tm(n,γ)¹⁷²Tm", "updated": null, "kind": "capture", "target": "171Tm", "projectile": "n", "ejectile": "g", "product": "172Tm", "from": { "code": "171Tm", "A": 171, "Z": 69, "N": 102 }, "to": { "code": "172Tm", "A": 172, "Z": 69, "N": 103 }, "networks": [ "s-main" ], "families": [ "s-process" ], "importance": "major", "summary": "Radioactive thulium-171 captures a neutron. Measured for the first time in 2020, both by time of flight and by activation, it turned out to capture 2.6 times less readily than the general-purpose libraries JEFF-3.3 and ENDF/B-VIII said.", "role": "Thulium-171 lives about two years in the laboratory. In an AGB star it either decays into ytterbium-171 or captures a neutron and moves on to thulium-172, so how readily it captures sets how much ytterbium-171 the star makes. Stardust grains from AGB stars, found in meteorites, record that amount, and they can be compared with the models only if the capture is known.", "details": "The sample was produced at the ILL high-flux reactor and separated at PSI. At n_TOF the capture yield gave the first set of resonance parameters of ¹⁷¹Tm; at SARAF the liquid-lithium target LiLiT provided a quasi-Maxwellian spectrum for an activation that gave the MACS at kT = 30 keV directly, 384(40) mb, in agreement with the time-of-flight estimate. The value is 2.6 times lower than JEFF-3.3 and ENDF/B-VIII, 25% lower than Bao et al. (2000) and 1.6 times higher than KADoNiS v1; with it, AGB models make more ¹⁷¹Yb, closer to the presolar SiC grains (Guerrero et al. 2020).", "status": "improving", "statusNote": "Measured in 2020 by time of flight at n_TOF and by activation at SARAF; the MACS at 30 keV is known to about 10%.", "statusPlain": "Measured for the first time in 2020, at CERN and in Israel, to about 10%.", "keywords": [ "thulium-171", "Tm-171", "branch point", "ytterbium-171", "SARAF" ], "methods": [ "neutron-beams", "activation" ], "measurements": [ { "year": 2020, "facility": "n-tof", "lab": "", "method": "neutron-beams", "energy": "resolved resonances (neutron energy)", "note": "First resonance parameters of ¹⁷¹Tm, on a sample made at the ILL; the MACS extrapolated from them agrees with the activation value.", "refs": [ "guerrero2020" ], "lowestKeV": null, "luna": false }, { "year": 2020, "facility": "saraf-lilit", "lab": "", "method": "activation", "energy": "quasi-Maxwellian kT ≈ 30 keV", "note": "MACS at kT = 30 keV of 384(40) mb, 2.6 times below the JEFF-3.3 and ENDF/B-VIII evaluations.", "refs": [ "guerrero2020" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "bao2000", "dillmann2008" ], "rmatrix": [], "openQuestions": [], "facts": [], "related": [ "147Pm-ng-148Pm", "204Tl-ng-205Tl", "151Sm-ng-152Sm" ], "q": { "value": 6.235018100000005, "annihilation": false, "kinetic": 6.235018100000005 }, "gamow": [], "thermal": [ { "network": "s-main", "label": "AGB ¹³C pocket", "T9": 0.09, "kT": 7.7555997 }, { "network": "s-main", "label": "AGB thermal pulse", "T9": 0.27, "kT": 23.266799100000004 } ], "windowNote": "A neutron feels no Coulomb barrier, so there is no Gamow window: the relevant energies are those of the thermal distribution itself, around kT.", "halfLife": { "seconds": 60589297.91999999, "stable": false, "text": "1.92 yr" }, "productHalfLife": { "seconds": 228960, "stable": false, "text": "2.65 d" }, "references": [ "guerrero2020", "bao2000", "dillmann2008" ], "luna": false, "lunaYears": [] }, { "id": "197Au-ng-198Au", "hasFile": true, "label": "¹⁹⁷Au(n,γ)¹⁹⁸Au", "updated": null, "kind": "capture", "target": "197Au", "projectile": "n", "ejectile": "g", "product": "198Au", "from": { "code": "197Au", "A": 197, "Z": 79, "N": 118 }, "to": { "code": "198Au", "A": 198, "Z": 79, "N": 119 }, "networks": [ "s-main" ], "families": [ "s-process" ], "importance": "major", "summary": "Gold-197 captures a neutron. Its cross section is the yardstick: most stellar neutron-capture cross sections are measured relative to it.", "role": "Counting the neutrons that hit a sample is hard. It is much easier to put a thin gold foil beside the sample and compare how many captures happen in each. Gold has a single stable isotope, and the product, gold-198, is radioactive with a convenient half-life of a few days, so its captures can be counted afterwards by its γ-rays. Every measurement made in this way inherits the uncertainty of the gold cross section, which is why it has been measured again and again.", "details": "Ratynski and Käppeler (1988) activated gold in the quasi-Maxwellian neutron spectrum of ⁷Li(p,n)⁷Be at E(p) = 1912 keV, with the integrated flux from the ⁷Be activity of the target: 648 ± 10 mb at kT = 25 keV, and 582 ± 9 mb when extrapolated to kT = 30 keV, the value adopted as the astrophysical reference. Time-of-flight data later pointed to a slightly higher value: at n_TOF, 5–400 keV with C₆D₆ detectors and a total uncertainty of 3.9–6.7%, the MACS at 30 keV agrees with ENDF/B-VII.0 and is 4.7% above the activation value (Lederer et al. 2011); at GELINA, 3.5–84 keV normalized to the saturated 4.9 eV resonance, the results differ by more than 5% from the astrophysical reference (Massimi et al. 2014). The 2017 evaluation of the IAEA neutron data standards then adopted the Maxwellian-averaged cross section at kT = 30 keV as a standard in its own right, 620 ± 11 mb (Carlson et al. 2018), 6.5% above the 1988 reference.", "status": "well-known", "statusNote": "Known to a few per cent; a difference of about 5% between the 1988 activation reference and later time-of-flight data and evaluations has been the main open point.", "statusPlain": "Known to a few per cent, and used as the yardstick for most other captures; the main open point was a 5% difference between two kinds of measurement.", "keywords": [ "gold", "Au-197", "neutron standard", "MACS standard" ], "methods": [ "activation", "neutron-beams" ], "measurements": [ { "year": 1988, "facility": "karlsruhe-vdg", "lab": "", "method": "activation", "energy": "quasi-Maxwellian kT = 25 keV (E(p) = 1912 keV)", "note": "648 ± 10 mb at kT = 25 keV; 582 ± 9 mb extrapolated to 30 keV, the reference for stellar capture measurements.", "refs": [ "ratynski1988" ], "lowestKeV": null, "luna": false }, { "year": 2011, "facility": "n-tof", "lab": "", "method": "neutron-beams", "energy": "5–400 keV (neutron energy)", "note": "C₆D₆ detectors, total uncertainty 3.9–6.7%; MACS at 30 keV 4.7% above the activation value and in agreement with ENDF/B-VII.0.", "refs": [ "lederer2011" ], "lowestKeV": null, "luna": false }, { "year": 2014, "facility": "gelina", "lab": "", "method": "neutron-beams", "energy": "3.5–84 keV (neutron energy)", "note": "Two C₆D₆ detectors at about 13 m, total energy method, normalized to the 4.9 eV resonance; more than 5% from the astrophysical reference.", "refs": [ "massimi2014" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "carlson2018", "bao2000", "dillmann2014", "dillmann2008" ], "rmatrix": [], "openQuestions": [], "facts": [], "related": [ "151Sm-ng-152Sm", "209Bi-ng-210Bi", "56Fe-ng-57Fe" ], "q": { "value": 6.512318099999998, "annihilation": false, "kinetic": 6.512318099999998 }, "gamow": [], "thermal": [ { "network": "s-main", "label": "AGB ¹³C pocket", "T9": 0.09, "kT": 7.7555997 }, { "network": "s-main", "label": "AGB thermal pulse", "T9": 0.27, "kT": 23.266799100000004 } ], "windowNote": "A neutron feels no Coulomb barrier, so there is no Gamow window: the relevant energies are those of the thermal distribution itself, around kT.", "halfLife": null, "productHalfLife": { "seconds": 232816.896, "stable": false, "text": "2.69 d" }, "references": [ "ratynski1988", "lederer2011", "massimi2014", "carlson2018", "bao2000", "dillmann2014", "dillmann2008" ], "luna": false, "lunaYears": [] }, { "id": "204Tl-ng-205Tl", "hasFile": true, "label": "²⁰⁴Tl(n,γ)²⁰⁵Tl", "updated": null, "kind": "capture", "target": "204Tl", "projectile": "n", "ejectile": "g", "product": "205Tl", "from": { "code": "204Tl", "A": 204, "Z": 81, "N": 123 }, "to": { "code": "205Tl", "A": 205, "Z": 81, "N": 124 }, "networks": [ "s-main" ], "families": [ "s-process" ], "importance": "major", "summary": "Radioactive thallium-204 captures a neutron. It decides how much lead-204, the heaviest nucleus made only by the s-process, the stars make; it was measured for the first time in 2024.", "role": "Thallium-204 lives almost four years in the laboratory. If it decays, it becomes lead-204, which the r-process cannot make, so all of it in the Solar System comes from the s-process. If it captures a neutron first, the flow passes to thallium-205 and lead-204 is skipped. The share between the two sets the amount of lead-204, which is used to check how the s-process models share out lead among its isotopes.", "details": "The first measurement of ²⁰⁴Tl(n,γ) was made at n_TOF on a 9 mg sample produced at the ILL high-flux reactor. Combined with semi-empirical calculations, it gives a MACS of 580(168) mb at kT ≈ 8 keV and 260(90) mb at kT ≈ 30 keV, about 3% lower and 20% higher than the purely theoretical values used until then (Casanovas-Hoste et al. 2024).", "status": "uncertain", "statusNote": "One measurement (n_TOF, 2024), with uncertainties of about 30% at the stellar energies; before it, only theory.", "statusPlain": "Measured once, in 2024, on nine milligrams of radioactive thallium; known to about 30%.", "keywords": [ "thallium-204", "Tl-204", "lead-204", "Pb-204", "branch point" ], "methods": [ "neutron-beams" ], "measurements": [ { "year": 2024, "facility": "n-tof", "lab": "", "method": "neutron-beams", "energy": "neutron energies up to the keV region", "note": "9 mg sample made at the ILL; MACS 580(168) mb at kT ≈ 8 keV and 260(90) mb at kT ≈ 30 keV, with semi-empirical calculations.", "refs": [ "casanovashoste2024" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "bao2000", "dillmann2008" ], "rmatrix": [], "openQuestions": [], "facts": [ { "text": "Thallium-205 is stable on Earth, but stripped of all its electrons it decays to lead-205, with a half-life of 291 days measured in the GSI storage ring. In stars this turns a stable nucleus into a source of a radioactive clock of the early Solar System.", "refs": [ "leckenby2024" ] } ], "related": [ "209Bi-ng-210Bi", "171Tm-ng-172Tm", "197Au-ng-198Au" ], "q": { "value": 7.546018099999998, "annihilation": false, "kinetic": 7.546018099999998 }, "gamow": [], "thermal": [ { "network": "s-main", "label": "AGB ¹³C pocket", "T9": 0.09, "kT": 7.7555997 }, { "network": "s-main", "label": "AGB thermal pulse", "T9": 0.27, "kT": 23.266799100000004 } ], "windowNote": "A neutron feels no Coulomb barrier, so there is no Gamow window: the relevant energies are those of the thermal distribution itself, around kT.", "halfLife": { "seconds": 119379851.058, "stable": false, "text": "3.78 yr" }, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "casanovashoste2024", "bao2000", "dillmann2008", "leckenby2024" ], "luna": false, "lunaYears": [] }, { "id": "209Bi-ng-210Bi", "hasFile": true, "label": "²⁰⁹Bi(n,γ)²¹⁰Bi", "updated": null, "kind": "capture", "target": "209Bi", "projectile": "n", "ejectile": "g", "product": "210Bi", "from": { "code": "209Bi", "A": 209, "Z": 83, "N": 126 }, "to": { "code": "210Bi", "A": 210, "Z": 83, "N": 127 }, "networks": [ "s-main" ], "families": [ "s-process" ], "importance": "major", "summary": "Bismuth-209 captures a neutron. It is the end of the s-process: what follows decays back to lead, and the path closes into a cycle.", "role": "Bismuth-209 is the heaviest nucleus the s-process reaches. When it captures a neutron it becomes bismuth-210, in one of two forms. The ground state decays within days to polonium-210, which emits an alpha particle and becomes lead-206; a long-lived excited form, the isomer, also ends as lead-206, through an alpha decay to thallium-206. The neutrons that reach bismuth therefore keep cycling through lead and bismuth instead of building anything heavier. The cross section decides how much of the bismuth in the Solar System the s-process made, and so how much is left for the rapid r-process to explain.", "details": "Capture on ²⁰⁹Bi feeds both the 5.0 d ground state of ²¹⁰Bi, which β⁻-decays to ²¹⁰Po, and a long-lived isomer (t½ ≈ 3 × 10⁶ yr in the laboratory). Activation at Karlsruhe measured the stellar cross sections of ²⁰⁸Pb and ²⁰⁹Bi at the termination of the path and the partial cross section to the ground state (Ratzel et al. 2004). Both states close the cycle at ²⁰⁶Pb: the ground state through ²¹⁰Po (138 d) and its α decay, the 271 keV isomer through its own α decay to ²⁰⁶Tl and β⁻ decay to ²⁰⁶Pb. Both branch: ²¹⁰Po can capture a neutron (²¹¹Po → ²⁰⁷Pb), and capture on the isomer gives ²¹¹Bi (α, 2.14 min → ²⁰⁷Tl → ²⁰⁷Pb), so part of the cycle leaks to ²⁰⁷Pb, by an amount that depends on the neutron density and the temperature (Domingo-Pardo et al. 2006). ²⁰⁹Bi itself is only quasi-stable: it α-decays with t½ ≈ 2 × 10¹⁹ yr. The capture resonances of ²⁰⁹Bi were measured at n_TOF with the pulse-height weighting technique, with a set-up of practically negligible neutron sensitivity. In the stellar range kT = 5–8 keV the new rate is about 16% higher than the value used before; the s-process fraction of solar bismuth becomes 19 ± 3%, leaving an r-process residual of 81 ± 3% (Domingo-Pardo et al. 2006).", "status": "improving", "statusNote": "The resonance data were revised at n_TOF in 2006, raising the stellar rate at low temperatures by about 16%.", "statusPlain": "Measured with neutron beams; a 2006 measurement at CERN raised the rate at the lowest stellar temperatures by about 16%.", "keywords": [ "bismuth", "lead–bismuth cycle", "Pb–Bi cycle", "isomer", "end of the s-process" ], "methods": [ "neutron-beams", "activation" ], "measurements": [ { "year": 2004, "facility": "karlsruhe-vdg", "lab": "", "method": "activation", "energy": "quasi-Maxwellian kT = 25 keV", "note": "Stellar cross sections of ²⁰⁸Pb and ²⁰⁹Bi at the end of the path; the partial cross section to the ²¹⁰Bi ground state, which feeds ²¹⁰Po.", "refs": [ "ratzel2004" ], "lowestKeV": null, "luna": false }, { "year": 2006, "facility": "n-tof", "lab": "", "method": "neutron-beams", "energy": "resolved resonances (neutron energy)", "note": "Pulse-height weighting with low neutron sensitivity; rate at kT = 5–8 keV about 16% higher; s fraction of solar Bi 19 ± 3%.", "refs": [ "domingopardo2006" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "bao2000", "dillmann2014", "dillmann2008" ], "rmatrix": [], "openQuestions": [], "facts": [], "related": [ "197Au-ng-198Au", "151Sm-ng-152Sm" ], "q": { "value": 4.604618099999998, "annihilation": false, "kinetic": 4.604618099999998 }, "gamow": [], "thermal": [ { "network": "s-main", "label": "AGB ¹³C pocket", "T9": 0.09, "kT": 7.7555997 }, { "network": "s-main", "label": "AGB thermal pulse", "T9": 0.27, "kT": 23.266799100000004 } ], "windowNote": "A neutron feels no Coulomb barrier, so there is no Gamow window: the relevant energies are those of the thermal distribution itself, around kT.", "halfLife": null, "productHalfLife": { "seconds": 433036.8, "stable": false, "text": "5.01 d" }, "references": [ "ratzel2004", "domingopardo2006", "bao2000", "dillmann2014", "dillmann2008" ], "luna": false, "lunaYears": [] }, { "id": "62Ni-ng-63Ni", "hasFile": true, "label": "⁶²Ni(n,γ)⁶³Ni", "updated": null, "kind": "capture", "target": "62Ni", "projectile": "n", "ejectile": "g", "product": "63Ni", "from": { "code": "62Ni", "A": 62, "Z": 28, "N": 34 }, "to": { "code": "63Ni", "A": 63, "Z": 28, "N": 35 }, "networks": [ "s-weak" ], "families": [ "s-process" ], "importance": "major", "summary": "Nickel-62 captures a neutron. In massive stars this capture is one of the steps that hold back the weak s-process, and it affects what is made after it.", "role": "In massive stars there are too few neutrons per iron seed for the s-process to reach far, and the flow of matter stays in the region from iron to strontium. There, each capture with a small cross section holds back the flow and lowers the production of every heavier nucleus. Nickel-62 is one of these steps, which is why its stellar cross section, in particular at the high temperatures of carbon-burning shells, changes the predicted production of the heavier nuclei, and of copper in particular.", "details": "At n_TOF the capture kernels of 42 resonances of ⁶²Ni were analysed up to 200 keV, and Maxwellian-averaged cross sections were calculated for kT = 5–100 keV with a total uncertainty of 4.5%. They agree with the KADoNiS value at kT = 30 keV but are up to a factor 1.6 lower at higher temperatures, which matters for shell carbon burning at kT ≈ 90 keV (Lederer et al. 2014).", "status": "improving", "statusNote": "Known to 4.5% at kT = 30 keV from n_TOF; the n_TOF data lowered the cross section at the higher temperatures of carbon burning by up to a factor 1.6.", "statusPlain": "Known to about 5%, from neutron-beam measurements at CERN, which lowered the value for the hottest burning in massive stars.", "keywords": [], "methods": [ "neutron-beams" ], "measurements": [ { "year": 2014, "facility": "n-tof", "lab": "", "method": "neutron-beams", "energy": "resonances up to 200 keV (neutron energy)", "note": "42 resonances analysed; MACS for kT = 5–100 keV with 4.5% total uncertainty, up to a factor 1.6 below KADoNiS at high kT.", "refs": [ "lederer2014" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "bao2000", "dillmann2008" ], "rmatrix": [], "openQuestions": [], "facts": [], "related": [ "63Ni-ng-64Ni", "56Fe-ng-57Fe", "22Ne-an-25Mg" ], "q": { "value": 6.837818100000007, "annihilation": false, "kinetic": 6.837818100000007 }, "gamow": [], "thermal": [ { "network": "s-weak", "label": "massive star, core helium burning", "T9": 0.3, "kT": 25.851999 }, { "network": "s-weak", "label": "massive star, shell carbon burning", "T9": 1.04, "kT": 89.62026320000001 } ], "windowNote": "A neutron feels no Coulomb barrier, so there is no Gamow window: the relevant energies are those of the thermal distribution itself, around kT.", "halfLife": null, "productHalfLife": { "seconds": 3193560911.2, "stable": false, "text": "101 yr" }, "references": [ "lederer2014", "bao2000", "dillmann2008" ], "luna": false, "lunaYears": [] }, { "id": "63Ni-ng-64Ni", "hasFile": true, "label": "⁶³Ni(n,γ)⁶⁴Ni", "updated": null, "kind": "capture", "target": "63Ni", "projectile": "n", "ejectile": "g", "product": "64Ni", "from": { "code": "63Ni", "A": 63, "Z": 28, "N": 35 }, "to": { "code": "64Ni", "A": 64, "Z": 28, "N": 36 }, "networks": [ "s-weak" ], "families": [ "s-process" ], "importance": "key", "summary": "Radioactive nickel-63 captures a neutron before it can decay. It is an early branch point of the s-process, and it decides how much copper massive stars make.", "role": "Nickel-63 lives about a century in the laboratory. In a massive star it can either decay into copper-63 or capture another neutron and become nickel-64; which of the two happens more often depends on how many neutrons are around and on this cross section. Massive stars are the main source of the copper in the Solar System, so the branching at nickel-63 shapes the copper, nickel and zinc they make. Measuring the reaction needs a radioactive sample, which is why it was first measured only in 2013.", "details": "Before 2013 the stellar cross section rested on calculations and extrapolations; KADoNiS recommended 31 ± 6 mb at kT = 30 keV. The first measurement, at n_TOF, covered thermal energies up to 200 keV, determined the capture kernels of 12 new resonances and gave MACS for kT = 5–100 keV with uncertainties around 20%; models of a 25 M☉ star showed a significant effect on the s-process production of ⁶³Cu, ⁶⁴Ni and ⁶⁴Zn (Lederer et al. 2013). Unresolved cross sections from 10 to 270 keV, with a systematic uncertainty of 17%, followed (Lederer et al. 2014). At LANSCE the calorimetric 4π BaF₂ array DANCE measured the cross section relative to ¹⁹⁷Au with uncertainties below 15% (Weigand et al. 2015).", "status": "improving", "statusNote": "Measured since 2013 on a radioactive sample at n_TOF and DANCE, with uncertainties of 15–20%.", "statusPlain": "Measured only since 2013, on a small radioactive sample; known to 15–20%.", "keywords": [], "methods": [ "neutron-beams" ], "measurements": [ { "year": 2013, "facility": "n-tof", "lab": "", "method": "neutron-beams", "energy": "thermal to 200 keV (neutron energy)", "note": "First measurement; 12 new resonances; MACS for kT = 5–100 keV with uncertainties around 20%.", "refs": [ "lederer2013" ], "lowestKeV": null, "luna": false }, { "year": 2014, "facility": "n-tof", "lab": "", "method": "neutron-beams", "energy": "10–270 keV (neutron energy)", "note": "Unresolved cross sections with a systematic uncertainty of 17%, published together with ⁶²Ni(n,γ).", "refs": [ "lederer2014" ], "lowestKeV": null, "luna": false }, { "year": 2015, "facility": "lansce-dance", "lab": "", "method": "neutron-beams", "energy": "neutron time of flight, relative to ¹⁹⁷Au", "note": "Cross section with the 4π BaF₂ calorimeter DANCE, uncertainties below 15%; resonances identified by their Q-value; network sensitivity studied.", "refs": [ "weigand2015" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "bao2000", "dillmann2008" ], "rmatrix": [], "openQuestions": [], "facts": [], "related": [ "62Ni-ng-63Ni", "56Fe-ng-57Fe", "85Kr-ng-86Kr" ], "q": { "value": 9.657418100000001, "annihilation": false, "kinetic": 9.657418100000001 }, "gamow": [], "thermal": [ { "network": "s-weak", "label": "massive star, core helium burning", "T9": 0.3, "kT": 25.851999 }, { "network": "s-weak", "label": "massive star, shell carbon burning", "T9": 1.04, "kT": 89.62026320000001 } ], "windowNote": "A neutron feels no Coulomb barrier, so there is no Gamow window: the relevant energies are those of the thermal distribution itself, around kT.", "halfLife": { "seconds": 3193560911.2, "stable": false, "text": "101 yr" }, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "lederer2013", "lederer2014", "weigand2015", "bao2000", "dillmann2008" ], "luna": false, "lunaYears": [] }, { "id": "1H-ng-2H", "hasFile": true, "label": "¹H(n,γ)²H", "updated": null, "kind": "capture", "target": "1H", "projectile": "n", "ejectile": "g", "product": "2H", "from": { "code": "1H", "A": 1, "Z": 1, "N": 0 }, "to": { "code": "2H", "A": 2, "Z": 1, "N": 1 }, "networks": [ "bbn" ], "families": [ "bbn" ], "importance": "major", "summary": "A neutron and a proton bind into a deuteron and give off a γ-ray. This is the first step of Big Bang nucleosynthesis: all later reactions start from the deuterium it makes.", "role": "In the first minutes after the Big Bang, neutrons and protons combined into deuterons almost as fast as energetic photons broke them apart again. Only when the Universe had cooled enough did deuterium survive, and the build-up of heavier nuclei could begin. The rate of this capture therefore sets when nucleosynthesis starts and how many neutrons are still left, which in turn fixes the amount of helium.", "details": "At BBN energies the capture is dominated by the isovector M1 transition from the ¹S₀ continuum at the lowest energies and by isovector E1 capture from P waves at higher energies. The cross section is calculated in pionless effective field theory, with the M1 amplitude to next-to-next-to-leading order and the E1 amplitude to N4LO; one counterterm is fixed by the cold neutron capture rate and another by deuteron photodisintegration data. The stated accuracy is 1% for centre-of-mass energies up to about 1 MeV.", "status": "well-known", "statusNote": "Calculated to about 1% at the energies of the Big Bang, with a theory tied to measurements of slow-neutron capture and of deuterons broken up by γ-rays.", "statusPlain": "Calculated to about 1% at the energies of the Big Bang, with a theory checked against laboratory measurements.", "keywords": [], "methods": [ "theory" ], "measurements": [ { "year": 2000, "facility": null, "lab": "", "method": "theory", "energy": "up to about 1 MeV", "note": "Pionless effective field theory calculation with M1 to NNLO and E1 to N4LO, constrained by the cold-neutron capture rate and by deuteron photodisintegration; 1% accuracy over the BBN range.", "refs": [ "rupak2000" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "fields2020" ], "rmatrix": [], "openQuestions": [], "facts": [], "related": [ "2H-pg-3He", "2H-dn-3He", "2H-dp-3H" ], "q": { "value": 2.2245662689999985, "annihilation": false, "kinetic": 2.2245662689999985 }, "gamow": [], "thermal": [ { "network": "bbn", "label": "deuterium bottleneck", "T9": 0.8, "kT": 68.93866400000002 }, { "network": "bbn", "label": "end of BBN", "T9": 0.3, "kT": 25.851999 } ], "windowNote": "A neutron feels no Coulomb barrier, so there is no Gamow window: the relevant energies are those of the thermal distribution itself, around kT.", "halfLife": null, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "rupak2000", "fields2020" ], "luna": false, "lunaYears": [] }, { "id": "2H-dn-3He", "hasFile": true, "label": "²H(d,n)³He", "updated": null, "kind": "fusion", "target": "2H", "projectile": "2H", "ejectile": "n", "product": "3He", "from": { "code": "2H", "A": 2, "Z": 1, "N": 1 }, "to": { "code": "3He", "A": 3, "Z": 2, "N": 1 }, "networks": [ "bbn" ], "families": [ "bbn" ], "importance": "major", "summary": "Two deuterons fuse into ³He and a neutron. Together with its twin reaction, which gives tritium and a proton, it is one of the main ways deuterium was destroyed after the Big Bang.", "role": "The deuterium left over from the Big Bang is a sensitive measure of the density of ordinary matter in the Universe. Three reactions decide how much deuterium burned: proton capture on deuterium and the two branches of deuteron–deuteron fusion. After the proton-capture rate was measured precisely at LUNA, the deuteron–deuteron rates became an important part of the remaining uncertainty.", "details": "The d+d reaction proceeds through two mirror channels of nearly equal strength, ³He + n and ³H + p. Both have been measured with accelerators over the BBN energy range and down to a few keV, where electron screening in laboratory targets becomes visible, and with the Trojan Horse method. The evaluations differ in how they weight and normalize these data sets, and analyses after the LUNA d(p,γ)³He result examine the effect of the d+d rates and of their evaluation on the predicted primordial deuterium abundance.", "status": "improving", "statusNote": "Several data sets exist, but the choice of evaluation changes the predicted primordial deuterium abundance noticeably.", "statusPlain": "", "keywords": [], "methods": [ "direct-surface", "thm" ], "measurements": [ { "year": 1995, "facility": null, "lab": "", "method": "direct-surface", "energy": "1.6–130 keV", "note": "Both d+d channels measured with beams from 30, 100 and 450 kV accelerators. The ratio of the two cross sections stays close to unity at low energy, so no Oppenheimer–Phillips effect was seen, and the electron-screening enhancement of d(d,p)t below 10 keV is larger than atomic-physics models predict.", "refs": [ "greife1995" ], "lowestKeV": null, "luna": false }, { "year": 2006, "facility": null, "lab": "TUNL Low-Energy Beam Facility, Durham NC", "method": "direct-surface", "energy": "110–650 keV (laboratory)", "note": "Total cross sections of both channels from a simultaneous fit of angular distributions and normalization data, with about 2% uncertainty and a 1% scale error; the resulting rates are about 7% above NACRE.", "refs": [ "leonard2006" ], "lowestKeV": null, "luna": false }, { "year": 2014, "facility": null, "lab": "", "method": "thm", "energy": "BBN energies", "note": "Trojan Horse determination of the bare S-factors of both channels, free of electron screening, and new reaction rates for BBN.", "refs": [ "tumino2014" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "descouvemont2004", "bosch1992", "pisanti2021", "fields2020" ], "rmatrix": [], "openQuestions": [ "The normalization of the S-factor at BBN energies, where the evaluations differ." ], "facts": [], "related": [ "2H-dp-3H", "2H-pg-3He", "3He-dp-4He" ], "q": { "value": 3.2689088100000028, "annihilation": false, "kinetic": 3.2689088100000028 }, "gamow": [ { "network": "bbn", "label": "deuterium bottleneck", "T9": 0.8, "E0": 105.38293609852634, "width": 196.84841552085624 }, { "network": "bbn", "label": "end of BBN", "T9": 0.3, "E0": 54.8013351510643, "width": 86.92765815934861 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "greife1995", "leonard2006", "tumino2014", "descouvemont2004", "bosch1992", "pisanti2021", "fields2020" ], "luna": false, "lunaYears": [] }, { "id": "2H-dp-3H", "hasFile": true, "label": "²H(d,p)³H", "updated": null, "kind": "fusion", "target": "2H", "projectile": "2H", "ejectile": "1H", "product": "3H", "from": { "code": "2H", "A": 2, "Z": 1, "N": 1 }, "to": { "code": "3H", "A": 3, "Z": 1, "N": 2 }, "networks": [ "bbn" ], "families": [ "bbn" ], "importance": "major", "summary": "Two deuterons fuse into tritium and a proton. It is the twin of the reaction that gives ³He and a neutron, and it also destroyed deuterium after the Big Bang.", "role": "This branch burns deuterium and makes tritium, which later decays to ³He or fuses with another deuteron. With proton capture on deuterium and the neutron branch of deuteron–deuteron fusion, it sets the amount of deuterium left from the Big Bang, which astronomers use to measure the density of ordinary matter.", "details": "The proton branch is easier to measure than the neutron branch, since the charged products can be detected with silicon detectors at the same time as the ³He from the mirror channel. Below 10 keV the data show an electron-screening enhancement larger than atomic-physics models predict. At BBN energies the TUNL measurement of 2006 gave rates about 7% above the NACRE compilation, and a Trojan Horse experiment determined the bare S-factor. As for ²H(d,n)³He, the normalization of the data sets at BBN energies and the choice of evaluation are the main open issues for primordial deuterium.", "status": "improving", "statusNote": "Measured over the whole BBN range, but the choice of evaluation matters for the deuterium prediction.", "statusPlain": "", "keywords": [], "methods": [ "direct-surface", "thm" ], "measurements": [ { "year": 1995, "facility": null, "lab": "", "method": "direct-surface", "energy": "1.6–130 keV", "note": "Both d+d channels measured with beams from 30, 100 and 450 kV accelerators. The ratio of the two cross sections stays close to unity at low energy, so no Oppenheimer–Phillips effect was seen, and the electron-screening enhancement of d(d,p)t below 10 keV is larger than atomic-physics models predict.", "refs": [ "greife1995" ], "lowestKeV": null, "luna": false }, { "year": 2006, "facility": null, "lab": "TUNL Low-Energy Beam Facility, Durham NC", "method": "direct-surface", "energy": "110–650 keV (laboratory)", "note": "Total cross sections of both channels from a simultaneous fit of angular distributions and normalization data, with about 2% uncertainty and a 1% scale error; the resulting rates are about 7% above NACRE.", "refs": [ "leonard2006" ], "lowestKeV": null, "luna": false }, { "year": 2014, "facility": null, "lab": "", "method": "thm", "energy": "BBN energies", "note": "Trojan Horse determination of the bare S-factors of both channels, free of electron screening, and new reaction rates for BBN.", "refs": [ "tumino2014" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "descouvemont2004", "bosch1992", "pisanti2021", "fields2020" ], "rmatrix": [], "openQuestions": [ "The normalization of the S-factor at BBN energies." ], "facts": [], "related": [ "2H-dn-3He", "3H-dn-4He", "2H-pg-3He" ], "q": { "value": 4.032663826000002, "annihilation": false, "kinetic": 4.032663826000002 }, "gamow": [ { "network": "bbn", "label": "deuterium bottleneck", "T9": 0.8, "E0": 105.38293609852634, "width": 196.84841552085624 }, { "network": "bbn", "label": "end of BBN", "T9": 0.3, "E0": 54.8013351510643, "width": 86.92765815934861 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": 388781328.32, "stable": false, "text": "12.3 yr" }, "references": [ "greife1995", "leonard2006", "tumino2014", "descouvemont2004", "bosch1992", "pisanti2021", "fields2020" ], "luna": false, "lunaYears": [] }, { "id": "3H-dn-4He", "hasFile": true, "label": "³H(d,n)⁴He", "updated": null, "kind": "fusion", "target": "3H", "projectile": "2H", "ejectile": "n", "product": "4He", "from": { "code": "3H", "A": 3, "Z": 1, "N": 2 }, "to": { "code": "4He", "A": 4, "Z": 2, "N": 2 }, "networks": [ "bbn" ], "families": [ "bbn" ], "importance": "minor", "summary": "Tritium and a deuteron fuse into ⁴He and a neutron. After the Big Bang it turned tritium into helium; on Earth it is the reaction planned for fusion power plants.", "role": "The tritium made by deuteron fusion after the Big Bang was mostly turned into ⁴He by this reaction. Its rate is so high that it does not limit the predicted abundances. Because the same reaction powers fusion experiments, its cross section is among the best studied in nuclear physics.", "details": "The cross section is dominated by a broad 3/2⁺ resonance in ⁵He just above the d+t threshold, which makes it very large at BBN energies. Bosch and Hale (1992) gave parametrizations of the cross section and of the Maxwellian reactivity, based on R-matrix calculations, that are widely used in fusion research, together with those of ²H(d,n)³He, ²H(d,p)³H and ³He(d,p)⁴He.", "status": "well-known", "statusNote": "Measured precisely for fusion-energy applications; its uncertainty does not affect BBN predictions.", "statusPlain": "", "keywords": [], "methods": [ "direct-surface", "theory" ], "measurements": [ { "year": 1992, "facility": null, "lab": "", "method": "theory", "energy": "", "note": "Parametrizations of the cross section and thermal reactivity based on R-matrix calculations; a correction followed in 1993.", "refs": [ "bosch1992" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "descouvemont2004", "bosch1992" ], "rmatrix": [], "openQuestions": [], "facts": [], "related": [ "2H-dp-3H", "3He-dp-4He", "3H-ag-7Li" ], "q": { "value": 17.589299825, "annihilation": false, "kinetic": 17.589299825 }, "gamow": [ { "network": "bbn", "label": "deuterium bottleneck", "T9": 0.8, "E0": 111.96082628628066, "width": 202.89896126834137 }, { "network": "bbn", "label": "end of BBN", "T9": 0.3, "E0": 58.2219758934042, "width": 89.59956065357598 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "bosch1992", "descouvemont2004" ], "luna": false, "lunaYears": [] }, { "id": "3He-dp-4He", "hasFile": true, "label": "³He(d,p)⁴He", "updated": null, "kind": "fusion", "target": "3He", "projectile": "2H", "ejectile": "1H", "product": "4He", "from": { "code": "3He", "A": 3, "Z": 2, "N": 1 }, "to": { "code": "4He", "A": 4, "Z": 2, "N": 2 }, "networks": [ "bbn" ], "families": [ "bbn" ], "importance": "minor", "summary": "³He and a deuteron fuse into ⁴He and a proton. After the Big Bang it converted part of the ³He into ⁴He.", "role": "The reaction is the mirror of deuterium–tritium fusion and, like it, is very fast at the energies of the early Universe. It removes ³He and deuterium and adds to ⁴He. In the laboratory it has been a favourite case for studying how the electrons around the target nuclei make fusion easier at low energy.", "details": "The cross section is dominated by the 3/2⁺ resonance in ⁵Li, the mirror of the ⁵He state that governs d+t. At the lowest energies the measured S-factor rises above the bare-nucleus trend because the atomic electrons of the target screen the Coulomb barrier. The LUNA 50 kV accelerator measured d(³He,p)⁴He down to 4.2 keV and found a screening potential of 132 ± 9 eV, twice the atomic-physics estimate of 65 eV. Measurements of both ³He(d,p)⁴He and d(³He,p)⁴He at a 100 kV accelerator in Bochum, with the LUNA setup, gave screening potentials of 219 ± 7 eV and 109 ± 9 eV, again well above the atomic-physics values of 120 eV and 65 eV. The Trojan Horse method, which gives the bare S-factor without screening, yielded a screening potential consistent with the adiabatic limit.", "status": "well-known", "statusNote": "Measured with small uncertainty at the energies of the Big Bang. The only open question is how much the atomic electrons of the target raise the measured rate at the lowest energies.", "statusPlain": "", "keywords": [], "methods": [ "direct-underground", "direct-surface", "thm" ], "measurements": [ { "year": 2000, "facility": "luna-50", "lab": "", "method": "direct-underground", "energy": "4.2–13.8 keV", "note": "d(³He,p)⁴He with a ³He beam on a deuterium gas target; the stopping power of ³He in D₂ agrees with the standard compilation, and the screening potential Uₑ = 132 ± 9 eV is twice the atomic-physics estimate.", "refs": [ "costantini2000" ], "lowestKeV": null, "luna": true }, { "year": 2001, "facility": null, "lab": "100 kV accelerator, Ruhr-Universität Bochum", "method": "direct-surface", "energy": "5–60 keV (d beam) and 10–40 keV (³He beam)", "note": "Both ³He(d,p)⁴He and d(³He,p)⁴He, with the LUNA setup; Uₑ = 219 ± 7 eV and 109 ± 9 eV, above the atomic-physics values of 120 and 65 eV.", "refs": [ "aliotta2001" ], "lowestKeV": null, "luna": false }, { "year": 2005, "facility": null, "lab": "", "method": "thm", "energy": "from 600 keV down to astrophysical energies", "note": "Trojan Horse measurement through the three-body reaction ⁶Li(³He,pα)⁴He at 5 and 6 MeV; the bare S-factor was extracted in the modified plane-wave Born approximation, and the screening potential derived from it is consistent with the adiabatic limit.", "refs": [ "lacognata2005" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "descouvemont2004", "bosch1992" ], "rmatrix": [], "openQuestions": [ "The electron-screening potential extracted from the lowest-energy direct data, which exceeds the adiabatic estimate, while the Trojan Horse analysis finds a value consistent with it." ], "facts": [], "related": [ "3H-dn-4He", "2H-dn-3He", "3He-3He2p-4He" ], "q": { "value": 18.353054841000002, "annihilation": false, "kinetic": 18.353054841000002 }, "gamow": [ { "network": "bbn", "label": "deuterium bottleneck", "T9": 0.8, "E0": 177.72657644689986, "width": 255.63655940675494 }, { "network": "bbn", "label": "end of BBN", "T9": 0.3, "E0": 92.42154414839847, "width": 112.88832267378842 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "costantini2000", "aliotta2001", "lacognata2005", "descouvemont2004", "bosch1992" ], "luna": true, "lunaYears": [ 2000 ] }, { "id": "3H-ag-7Li", "hasFile": true, "label": "³H(α,γ)⁷Li", "updated": null, "kind": "capture", "target": "3H", "projectile": "4He", "ejectile": "g", "product": "7Li", "from": { "code": "3H", "A": 3, "Z": 1, "N": 2 }, "to": { "code": "7Li", "A": 7, "Z": 3, "N": 4 }, "networks": [ "bbn" ], "families": [ "bbn" ], "importance": "minor", "summary": "Tritium captures a ⁴He nucleus and becomes ⁷Li, giving off a γ-ray. It made a small part of the primordial lithium; most of it came from ⁷Be.", "role": "At the baryon density measured today, most of the ⁷Li produced after the Big Bang was first made as ⁷Be, through the mirror reaction on ³He, and decayed to ⁷Li later. This reaction makes ⁷Li directly and contributes a smaller share. It is also a test case for nuclear models, which must describe it together with its mirror.", "details": "The reaction is the mirror of ³He(α,γ)⁷Be: an external direct capture to the ground and first excited states of ⁷Li. Its lower Coulomb barrier allows measurements at lower energy, but the radioactive tritium target or beam complicates the experiments. The Caltech measurement of 1994 covered 50–1200 keV, measured a branching ratio between the two γ transitions that is nearly independent of energy, and found an S-factor below 150 keV considerably smaller than earlier experiments had indicated.", "status": "improving", "statusNote": "Measured at BBN energies with uncertainties that affect only the small directly produced share of primordial ⁷Li.", "statusPlain": "", "keywords": [], "methods": [ "direct-surface" ], "measurements": [ { "year": 1994, "facility": "kellogg", "lab": "", "method": "direct-surface", "energy": "50–1200 keV", "note": "Absolute cross section and a branching ratio between the two γ transitions of about 0.45, nearly independent of energy; below 150 keV the S-factor is considerably smaller than earlier data indicated.", "refs": [ "brune1994" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "descouvemont2004" ], "rmatrix": [], "openQuestions": [], "facts": [], "related": [ "3He-ag-7Be", "7Li-pa-4He", "3H-dn-4He" ], "q": { "value": 2.467621769999999, "annihilation": false, "kinetic": 2.467621769999999 }, "gamow": [ { "network": "bbn", "label": "deuterium bottleneck", "T9": 0.8, "E0": 199.96265634605155, "width": 271.15725257890085 }, { "network": "bbn", "label": "end of BBN", "T9": 0.3, "E0": 103.98477166997723, "width": 119.74221330275053 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "brune1994", "descouvemont2004" ], "luna": false, "lunaYears": [] }, { "id": "7Be-np-7Li", "hasFile": true, "label": "⁷Be(n,p)⁷Li", "updated": null, "kind": "transfer", "target": "7Be", "projectile": "n", "ejectile": "1H", "product": "7Li", "from": { "code": "7Be", "A": 7, "Z": 4, "N": 3 }, "to": { "code": "7Li", "A": 7, "Z": 3, "N": 4 }, "networks": [ "bbn" ], "families": [ "bbn" ], "importance": "major", "summary": "A ⁷Be nucleus absorbs a neutron and becomes ⁷Li, emitting a proton. After the Big Bang it was the main reaction that destroyed ⁷Be, and with it much of the future lithium.", "role": "Most of the primordial lithium was first made as ⁷Be, which turned into ⁷Li only after the nucleosynthesis was over. Any ⁷Be destroyed earlier lowers the lithium predicted today. This reaction removed the largest share. Because the predicted lithium is higher than the amount seen in old stars, its rate has been re-measured to check whether a larger value could close the gap.", "details": "The reaction has a large cross section at thermal energies and follows a 1/v trend up to resonances in ⁸Be at higher neutron energies. BBN needs neutron energies of tens of keV. Direct measurements combine radioactive ⁷Be targets with neutron time-of-flight beams. Before 2018 the only two data sets from thermal to keV energies dated from the 1980s, did not reach the BBN window and disagreed with each other. The n_TOF measurement at CERN, with a ⁷Be target implanted at ISOLDE, covered neutron energies from thermal up to about 325 keV. Its cross section is higher than the evaluations at low energy and agrees with values inferred from the time-reversed ⁷Li(p,n)⁷Be reaction, but the change reduces the predicted primordial lithium only slightly. A Trojan Horse measurement with a ⁷Be beam (Hayakawa et al. 2021) separated the (n,p₀) and (n,p₁) channels and quantified the transition to the first excited state of ⁷Li at BBN energies for the first time; including it lowers the predicted ⁷Li by about a tenth, still far from the factor of about three that the lithium problem needs.", "status": "improving", "statusNote": "Time-of-flight data now cover the BBN energies; the higher cross section they give is far from enough to solve the lithium problem.", "statusPlain": "", "keywords": [], "methods": [ "neutron-beams", "thm" ], "measurements": [ { "year": 1988, "facility": null, "lab": "LANSCE, Los Alamos National Laboratory, Los Alamos NM", "method": "neutron-beams", "energy": "25 meV to 13.5 keV (neutron energy)", "note": "Time-of-flight measurement with a ⁷Be sample, normalized to the thermal cross section measured at the Omega West Reactor; it stops below the BBN energies.", "refs": [ "koehler1988" ], "lowestKeV": null, "luna": false }, { "year": 2018, "facility": "n-tof", "lab": "", "method": "neutron-beams", "energy": "thermal to about 325 keV (neutron energy)", "note": "High-purity ⁷Be target implanted at ISOLDE, the EAR2 flight path and a silicon telescope; the cross section is higher than the evaluations at low energy and agrees with ⁷Li(p,n)⁷Be data. The effect on the lithium problem is minor.", "refs": [ "damone2018" ], "lowestKeV": null, "luna": false }, { "year": 2021, "facility": null, "lab": "CRIB radioactive-beam separator, Japan", "method": "thm", "energy": "BBN energies (via ⁷Be(d,⁷Li p)¹H and ⁷Be(d,αα)¹H)", "note": "Trojan Horse measurement of ⁷Be(n,p)⁷Li and ⁷Be(n,α)⁴He at the same time; an improved (n,p₀) cross section and the first quantification of the (n,p₁) channel in the BBN energy region, which in the PRIMAT code lowers the predicted ⁷Li by about a tenth.", "refs": [ "hayakawa2021" ], "lowestKeV": null, "luna": false } ], "evaluations": [ "descouvemont2004", "iliadis2020" ], "rmatrix": [], "openQuestions": [ "The contribution of transitions to the first excited state of ⁷Li at BBN energies, which the total cross-section measurements of 1988 and 2018 do not separate; the 2021 Trojan Horse data give a first value, still to be confirmed by a direct measurement." ], "facts": [], "related": [ "3He-ag-7Be", "7Be-ec-7Li", "7Li-pa-4He" ], "q": { "value": 1.6442420359999979, "annihilation": false, "kinetic": 1.6442420359999979 }, "gamow": [], "thermal": [ { "network": "bbn", "label": "deuterium bottleneck", "T9": 0.8, "kT": 68.93866400000002 }, { "network": "bbn", "label": "end of BBN", "T9": 0.3, "kT": 25.851999 } ], "windowNote": "A neutron feels no Coulomb barrier, so there is no Gamow window: the relevant energies are those of the thermal distribution itself, around kT.", "halfLife": { "seconds": 4598208, "stable": false, "text": "53.2 d" }, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "koehler1988", "damone2018", "hayakawa2021", "descouvemont2004", "iliadis2020" ], "luna": false, "lunaYears": [] }, { "id": "2H-ag-6Li", "hasFile": true, "label": "²H(α,γ)⁶Li", "updated": null, "kind": "capture", "target": "2H", "projectile": "4He", "ejectile": "g", "product": "6Li", "from": { "code": "2H", "A": 2, "Z": 1, "N": 1 }, "to": { "code": "6Li", "A": 6, "Z": 3, "N": 3 }, "networks": [ "bbn" ], "families": [ "bbn" ], "importance": "minor", "summary": "A deuteron captures a ⁴He nucleus and becomes ⁶Li, giving off a γ-ray. It is the only way the Big Bang made the lighter lithium isotope.", "role": "Standard Big Bang nucleosynthesis predicts very little ⁶Li, far less than ⁷Li. Some observations of old stars once suggested much more, which would have pointed to new physics or to other sources of ⁶Li. The rate of this reaction at the energies of the early Universe tells whether the Big Bang alone could have made that much. It is very hard to measure because it happens so rarely; the first direct measurement, deep underground at LUNA, found a rate too low to explain the reported amounts.", "details": "The electric-dipole (E1) transition is suppressed by isospin selection rules and by the equal charge-to-mass ratios of the deuteron and the alpha particle, so the capture at BBN energies proceeds through E2 and a residual E1 component, and the cross section is very small. At higher energy the 3⁺ first excited state of ⁶Li appears as a resonance. Direct measurements are limited by the neutron background from ²H(d,n)³He, induced by deuterons that the beam scatters elastically in the target, and by the γ-ray background, which makes underground accelerators the natural place for them. The LUNA collaboration measured the cross section directly at the 400 kV accelerator under Gran Sasso, first at two BBN energies (2014) and then at four energies between 80 and 133 keV (2017). Coulomb dissociation of ⁶Li beams was used earlier, but nuclear break-up dominates at the relevant energies, so those data give only upper limits on the capture cross section.", "status": "improving", "statusNote": "Direct data at BBN energies come from a single underground experiment at four energies; the resulting rate is lower than earlier estimates.", "statusPlain": "", "keywords": [], "methods": [ "direct-underground", "coulomb-dissociation" ], "measurements": [ { "year": 1991, "facility": null, "lab": "Kernforschungszentrum Karlsruhe, Karlsruhe", "method": "coulomb-dissociation", "energy": "156 MeV ⁶Li beam", "note": "Coulomb dissociation of ⁶Li into α + d at very low relative energies; the deduced S-factor was almost constant below 400 keV, contrary to theoretical expectations.", "refs": [ "kiener1991" ], "lowestKeV": null, "luna": false }, { "year": 2010, "facility": "gsi", "lab": "", "method": "coulomb-dissociation", "energy": "⁶Li beam at 150 MeV/u", "note": "High-energy break-up of ⁶Li to test the Coulomb-dissociation approach; nuclear break-up dominates, so the data constrain the capture cross section only from above.", "refs": [ "hammache2010" ], "lowestKeV": null, "luna": false }, { "year": 2014, "facility": "luna-400", "lab": "", "method": "direct-underground", "energy": "two energies in the BBN range", "note": "First direct measurement at BBN energies. With standard BBN the data give a primordial ⁶Li/⁷Li ratio of (1.5 ± 0.3) × 10⁻⁵, far below the values reported for halo stars.", "refs": [ "anders2014" ], "lowestKeV": null, "luna": true }, { "year": 2017, "facility": "luna-400", "lab": "", "method": "direct-underground", "energy": "80, 93, 120 and 133 keV", "note": "Full LUNA data set and a new thermonuclear rate, lower than earlier estimates, which widens the gap between predicted and reported ⁶Li.", "refs": [ "trezzi2017" ], "lowestKeV": null, "luna": true } ], "evaluations": [ "descouvemont2004" ], "rmatrix": [], "openQuestions": [ "The size of the residual E1 contribution at BBN energies." ], "facts": [], "related": [ "2H-dn-3He", "2H-dp-3H", "3H-ag-7Li" ], "q": { "value": 1.4737583650000001, "annihilation": false, "kinetic": 1.4737583650000001 }, "gamow": [ { "network": "bbn", "label": "deuterium bottleneck", "T9": 0.8, "E0": 183.9902874133189, "width": 260.10231951472576 }, { "network": "bbn", "label": "end of BBN", "T9": 0.3, "E0": 95.67880511177876, "width": 114.86038867726721 } ], "thermal": [], "windowNote": null, "halfLife": null, "productHalfLife": { "seconds": null, "stable": true, "text": "stable" }, "references": [ "kiener1991", "hammache2010", "anders2014", "trezzi2017", "descouvemont2004" ], "luna": true, "lunaYears": [ 2014, 2017 ] } ], "references": { "patterson1969": { "key": "patterson1969", "authors": "J. R. Patterson, H. Winkler, C. S. Zaidins", "title": "Experimental investigation of the stellar nuclear reaction ¹²C + ¹²C at low energies", "journal": "Astrophys. J. 157, 367 (1969)", "year": 1969, "checked": "citation (authors, title, volume, page) from the reference lists of arXiv 1905.02054, 1810.07887 and nucl-ex/0702023; DOI not shown by any record found, so omitted, 2026-10-12" }, "mazarakis1973": { "key": "mazarakis1973", "authors": "M. G. Mazarakis, W. E. Stephens", "title": "Experimental measurements of the ¹²C + ¹²C nuclear reactions at low energies", "journal": "Phys. Rev. C 7, 1280 (1973)", "year": 1973, "doi": "10.1103/PhysRevC.7.1280", "checked": "APS Phys. Rev. C vol. 7 issue 4 listing and the reference lists of arXiv 2609.25996 and nucl-ex/0702023; DOI from the APS scheme, 2026-10-12" }, "high1977": { "key": "high1977", "authors": "M. D. High, B. Čujec", "title": "The ¹²C + ¹²C sub-Coulomb fusion cross section", "journal": "Nucl. Phys. A 282, 181 (1977)", "year": 1977, "doi": "10.1016/0375-9474(77)90179-8", "checked": "reference lists of arXiv 1905.02054 and 2507.18065 (with DOI) and IAEA EXFOR entry B0144 (in-beam γ-ray measurement at 90° and 270°), 2026-10-12" }, "becker1981": { "key": "becker1981", "authors": "H. W. Becker, K. U. Kettner, C. Rolfs, H. P. Trautvetter", "title": "The ¹²C + ¹²C reaction at subcoulomb energies (II)", "journal": "Z. Phys. A 303, 305 (1981)", "year": 1981, "doi": "10.1007/BF01421528", "checked": "reference list of arXiv 1905.02054 (authors, title, pages 305–312, DOI) and the summary in arXiv nucl-ex/0702023 of the early data sets reaching E ≈ 2.5 MeV, 2026-10-12" }, "spillane2007": { "key": "spillane2007", "authors": "T. Spillane, F. Raiola, C. Rolfs, F. Strieder, S. Zeng, H.-W. Becker et al.", "title": "Study of the ¹²C + ¹²C fusion reactions near the Gamow energy", "journal": "Phys. Rev. Lett. 98, 122501 (2007)", "year": 2007, "doi": "10.1103/PhysRevLett.98.122501", "arxiv": "nucl-ex/0702023", "checked": "arXiv nucl-ex/0702023 listing and abstract (E = 2.10–4.75 MeV, γ-ray spectroscopy, resonance at 2.14 MeV, factor 5 near 8×10⁸ K), Naples IRIS record; Bochum Dynamitron tandem from the search summary of the paper; DOI from the APS scheme, 2026-10-12" }, "bucher2015": { "key": "bucher2015", "authors": "B. Bucher, X. D. Tang, X. Fang et al.", "title": "First direct measurement of ¹²C(¹²C,n)²³Mg at stellar energies", "journal": "Phys. Rev. Lett. 114, 251102 (2015)", "year": 2015, "doi": "10.1103/PhysRevLett.114.251102", "arxiv": "1507.03980", "checked": "arXiv 1507.03980 listing and abstract, Monash and Hull repository records; Notre Dame FN tandem from the group's 2010 APS DNP abstract on the same study; DOI from the APS scheme, 2026-10-12" }, "zickefoose2018": { "key": "zickefoose2018", "authors": "J. Zickefoose, A. Di Leva, F. Strieder, L. Gialanella, G. Imbriani, N. De Cesare, C. Rolfs, J. Schweitzer, T. Spillane, O. Straniero, F. Terrasi", "title": "Measurement of the ¹²C(¹²C,p)²³Na cross section near the Gamow energy", "journal": "Phys. Rev. C 97, 065806 (2018)", "year": 2018, "doi": "10.1103/PhysRevC.97.065806", "checked": "JINA Virtual Journal entry and Naples IRIS record (authors, DOI, abstract), 2026-10-12" }, "aguilera2006": { "key": "aguilera2006", "authors": "E. F. Aguilera, P. Rosales, E. Martinez-Quiroz, G. Murillo, M. Fernández et al.", "title": "New γ-ray measurements for ¹²C + ¹²C sub-Coulomb fusion: toward data unification", "journal": "Phys. Rev. C 73, 064601 (2006)", "year": 2006, "doi": "10.1103/PhysRevC.73.064601", "checked": "TIB library record (title, authors, 2006, Phys. Rev. C) and the reference to it in arXiv 2006.06305 among the γ-ray measurements; article number as given in the round-2 review and consistent with the neighbouring record 064602; DOI from the APS scheme, 2026-10-12" }, "moralesgallegos2022": { "key": "moralesgallegos2022", "authors": "L. Morales-Gallegos, M. Aliotta, L. Gialanella et al.", "title": "Direct measurements of the ¹²C(¹²C,p)²³Na and ¹²C(¹²C,α)²⁰Ne reactions at low energies for nuclear astrophysics", "journal": "EPJ Web Conf. 260, 01006 (2022)", "year": 2022, "doi": "10.1051/epjconf/202226001006", "checked": "EPJ Web of Conferences abstract page and DOAJ record (CIRCE, Caserta; ΔE–E telescopes; E = 2.51–4.36 MeV in 10–25 keV steps); EPJ A retraction note seen in search results, 2026-10-12" }, "moralesgallegos2023r": { "key": "moralesgallegos2023r", "authors": "L. Morales-Gallegos, M. Aliotta, L. Gialanella et al.", "title": "Retraction Note: Direct measurements of the ¹²C + ¹²C reactions cross-sections towards astrophysical energies", "journal": "Eur. Phys. J. A 59, 120 (2023)", "year": 2023, "doi": "10.1140/epja/s10050-023-01022-7", "checked": "Springer and EPJ A pages for the DOI, by web search (retraction of Eur. Phys. J. A 58, 65 (2022) for an error in the script computing beam energy losses from tabulated stopping powers; general analysis and conclusions unchanged), 2026-10-13" }, "moralesgallegos2024": { "key": "moralesgallegos2024", "authors": "L. Morales-Gallegos et al.", "title": "Direct measurements of the ¹²C+¹²C reactions cross-sections towards astrophysical energies", "journal": "Eur. Phys. J. A 60, 11 (2024)", "year": 2024, "doi": "10.1140/epja/s10050-024-01233-6", "checked": "Springer article page, University of Edinburgh Research Explorer and INIS records (published 22 January 2024; CIRCE, E = 2.51–4.36 MeV; three angles, non-isotropic angular distributions), by web search, 2026-10-12" }, "zhang2020": { "key": "zhang2020", "authors": "N. T. Zhang et al.", "title": "Constraining the ¹²C + ¹²C astrophysical S-factors with the ¹²C + ¹³C measurements at very low energies", "journal": "Phys. Lett. B 801, 135170 (2020)", "year": 2020, "arxiv": "1909.07012", "checked": "arXiv 1909.07012 (ar5iv; ¹²C(¹³C,p)²⁴Na by activation down to E = 2.323 MeV, counted underground; upper limit on ¹²C + ¹²C; against the hindrance maximum), DOAJ record of the Phys. Lett. B article and the INL repository record; DOI not shown by the records, so omitted, 2026-10-12" }, "tumino2018": { "key": "tumino2018", "authors": "A. Tumino, C. Spitaleri, M. La Cognata, S. Cherubini, G. L. Guardo, M. Gulino, S. Hayakawa, I. Indelicato et al.", "title": "An increase in the ¹²C + ¹²C fusion rate from resonances at astrophysical energies", "journal": "Nature 557, 687 (2018)", "year": 2018, "doi": "10.1038/s41586-018-0149-4", "checked": "RePEc/IDEAS record (DOI, title, abstract), the publisher correction record (Nature 561, DOI 10.1038/s41586-018-0269-x) and the authors' reply arXiv 1807.06148 for the author list; LNS tandem and 30 MeV ¹⁴N beam from a Tumino conference talk, 2026-10-12" }, "mukhamedzhanov2019": { "key": "mukhamedzhanov2019", "authors": "A. M. Mukhamedzhanov, D. Y. Pang, A. S. Kadyrov", "title": "Astrophysical factors of ¹²C + ¹²C fusion extracted using the Trojan horse method", "journal": "Phys. Rev. C 99, 064618 (2019)", "year": 2019, "doi": "10.1103/PhysRevC.99.064618", "arxiv": "1806.08828", "checked": "APS accepted-manuscript page (title, authors, DOI, abstract) and the Texas A&M Cyclotron Institute progress reports 2018–2020, 2026-10-12" }, "fruet2020": { "key": "fruet2020", "authors": "G. Fruet, S. Courtin, M. Heine et al. (STELLA collaboration)", "title": "Advances in the direct study of carbon burning in massive stars", "journal": "Phys. Rev. Lett. 124, 192701 (2020)", "year": 2020, "doi": "10.1103/PhysRevLett.124.192701", "checked": "White Rose record 161875 with abstract and DOI, REF 2021 output records; Andromède facility from EPJ Web Conf. (HIAS 2025) 00029, 2026-10-12" }, "tan2020": { "key": "tan2020", "authors": "W. P. Tan et al.", "title": "New measurement of ¹²C + ¹²C fusion reaction at astrophysical energies", "journal": "Phys. Rev. Lett. 124, 192702 (2020)", "year": 2020, "doi": "10.1103/PhysRevLett.124.192702", "arxiv": "2005.03196", "checked": "arXiv 2005.03196 abstract (Notre Dame 5U Pelletron, SAND, particle–γ coincidences, disagreement with the Trojan Horse result), IAEA EXFOR entry C2574 and JINA Virtual Journal listing with DOI, 2026-10-12" }, "heine2018": { "key": "heine2018", "authors": "M. Heine et al.", "title": "The STELLA apparatus for particle-gamma coincidence fusion measurements with nanosecond timing", "journal": "Nucl. Instrum. Methods A 903, 1 (2018)", "year": 2018, "doi": "10.1016/j.nima.2018.06.058", "arxiv": "1802.07679", "checked": "HAL record hal-01724871, arXiv 1802.07679 and White Rose record 137500, 2026-10-12" }, "nippert2025": { "key": "nippert2025", "authors": "J. Nippert, S. Courtin, M. Heine, D. G. Jenkins, P. Adsley et al. (STELLA collaboration)", "title": "Refining the deep sub-barrier ¹²C + ¹²C fusion excitation function with the STELLA apparatus", "journal": "Phys. Rev. C 111, 065804 (2025)", "year": 2025, "doi": "10.1103/PhysRevC.111.065804", "arxiv": "2509.14717", "checked": "arXiv 2509.14717, HAL record hal-05104930 and White Rose record 234979 (DOI, abstract), 2026-10-12; abstract rechecked by web search (no confirmed overall rise of S at deep sub-barrier energies; p₁/α₁ branching ratio of about 2% at 3.23 MeV; lower average S between 2.2 and 2.6 MeV), 2026-10-13" }, "gesue2025": { "key": "gesue2025", "authors": "R. M. Gesuè, S. Turkat, J. Skowronski, M. Aliotta et al. (LUNA Collaboration)", "title": "Detector characterization for a new ¹²C + ¹²C reaction study at LUNA", "journal": "J. Phys. G 52, 105103 (2025)", "year": 2025, "doi": "10.1088/1361-6471/ade0dc", "arxiv": "2601.05285", "checked": "arXiv 2601.05285 listing and abstract, Naples IRIS record; journal reference as in content/publications.yaml, 2026-10-12" }, "caughlan1988": { "key": "caughlan1988", "authors": "G. R. Caughlan, W. A. Fowler", "title": "Thermonuclear reaction rates V", "journal": "At. Data Nucl. Data Tables 40, 283 (1988)", "year": 1988, "checked": "citation from arXiv 2406.13458 and 1012.3258 (the standard ¹²C + ¹²C rate of stellar models) and the online CF88 mirror; DOI not shown by any record found, so omitted, 2026-10-12" }, "jiang2007": { "key": "jiang2007", "authors": "C. L. Jiang et al.", "title": "Expectations for ¹²C and ¹⁶O induced fusion cross sections at energies of astrophysical interest", "journal": "Phys. Rev. C 75, 015803 (2007)", "year": 2007, "doi": "10.1103/PhysRevC.75.015803", "checked": "IAEA INIS record (title, journal, Argonne affiliation, abstract) and the summary in arXiv 2507.18065; DOI from the APS scheme, 2026-10-12" }, "jiang2018": { "key": "jiang2018", "authors": "C. L. Jiang, D. Santiago-Gonzalez, S. Almaraz-Calderon, K. E. Rehm et al.", "title": "Reaction rate for carbon burning in massive stars", "journal": "Phys. Rev. C 97, 012801 (2018)", "year": 2018, "doi": "10.1103/PhysRevC.97.012801", "checked": "APS accepted-manuscript page and INL repository record, 2026-10-12" }, "monpribat2022": { "key": "monpribat2022", "authors": "E. Monpribat, S. Martinet, S. Courtin, M. Heine, S. Ekström, D. G. Jenkins, A. Choplin et al.", "title": "A new ¹²C + ¹²C nuclear reaction rate: impact on stellar evolution", "journal": "Astron. Astrophys. 660, A47 (2022)", "year": 2022, "doi": "10.1051/0004-6361/202141858", "arxiv": "2111.15224", "checked": "arXiv 2111.15224, White Rose record 187718 and Texas A&M publication record with DOI, 2026-10-12" }, "uzawa2025": { "key": "uzawa2025", "authors": "K. Uzawa, K. Hagino", "title": "Re-examination of fusion hindrance in astrophysical ¹²C + ¹²C and ¹²C + ¹³C reactions", "journal": "Phys. Rev. C 112, L061601 (2025)", "year": 2025, "arxiv": "2507.18065", "checked": "arXiv 2507.18065 abstract; journal reference from K. Hagino's publication list (Yukawa Institute) and his 2026 talk slides, 2026-10-12; DOI searched again and not found, so removed, 2026-10-13" }, "woosley2002": { "key": "woosley2002", "authors": "S. E. Woosley, A. Heger, T. A. Weaver", "title": "The evolution and explosion of massive stars", "journal": "Rev. Mod. Phys. 74, 1015 (2002)", "year": 2002, "doi": "10.1103/RevModPhys.74.1015", "arxiv": "astro-ph/0110015", "checked": "arXiv astro-ph/0110015 listing and scinapse record with DOI; the carbon-burning row of its 15 M☉ table (T = 0.83 GK) as reproduced in the Utrecht stellar-evolution lecture notes, chapter 12, 2026-10-12" }, "pignatari2013": { "key": "pignatari2013", "authors": "M. Pignatari, R. Hirschi, M. Wiescher et al.", "title": "The ¹²C + ¹²C reaction and the impact on nucleosynthesis in massive stars", "journal": "Astrophys. J. 762, 31 (2013)", "year": 2013, "doi": "10.1088/0004-637X/762/1/31", "arxiv": "1212.3962", "checked": "arXiv 1212.3962 listing and Hull repository record 561935 (title, journal, 25 M☉ models with the three channels varied); DOI from the IOP scheme for ApJ 762, 31, 2026-10-12" }, "cooper2009": { "key": "cooper2009", "authors": "R. L. Cooper, A. W. Steiner, E. F. Brown", "title": "Possible resonances in the ¹²C + ¹²C fusion rate and superburst ignition", "journal": "Astrophys. J. 702, 660 (2009)", "year": 2009, "doi": "10.1088/0004-637X/702/1/660", "arxiv": "0903.3994", "checked": "arXiv 0903.3994 abstract (superbursts on accreting neutron stars; Gamow peak near 1.5 MeV; ignition temperature 6 × 10⁸ K, 5 × 10⁸ K with a resonance) and the DOI record, 2026-10-12" }, "formicola2004": { "key": "formicola2004", "authors": "A. Formicola et al. (LUNA Collaboration)", "title": "Astrophysical S-factor of ¹⁴N(p,γ)¹⁵O", "journal": "Phys. Lett. B 591, 61 (2004)", "year": 2004, "doi": "10.1016/j.physletb.2004.03.092", "arxiv": "nucl-ex/0312015", "luna": true, "checked": "arXiv nucl-ex/0312015 and DOI confirmed by search, 2026-10-11" }, "lemut2006": { "key": "lemut2006", "authors": "A. Lemut et al. (LUNA Collaboration)", "title": "First measurement of the ¹⁴N(p,γ)¹⁵O cross section down to 70 keV", "journal": "Phys. Lett. B 634, 483 (2006)", "year": 2006, "doi": "10.1016/j.physletb.2006.02.021", "arxiv": "nucl-ex/0602012", "luna": true, "checked": "arXiv nucl-ex/0602012 and DOI confirmed by search, 2026-10-11" }, "marta2011": { "key": "marta2011", "authors": "M. Marta et al. (LUNA Collaboration)", "title": "The ¹⁴N(p,γ)¹⁵O reaction studied with a composite germanium detector", "journal": "Phys. Rev. C 83, 045804 (2011)", "year": 2011, "doi": "10.1103/PhysRevC.83.045804", "arxiv": "1103.5393", "luna": true, "checked": "arXiv 1103.5393 and journal reference confirmed by search, 2026-10-11" }, "rolfs1974": { "key": "rolfs1974", "authors": "C. Rolfs and R. E. Azuma", "title": "Interference effects in ¹²C(p,γ)¹³N and direct capture to unbound states", "journal": "Nucl. Phys. A 227, 291 (1974)", "year": 1974, "doi": "10.1016/0375-9474(74)90798-2", "checked": "ScienceDirect record (PII 0375947474907982) and citations in later arXiv papers, by web search, 2026-10-11" }, "king1994": { "key": "king1994", "authors": "J. D. King, R. E. Azuma, J. B. Vise, J. Görres, C. Rolfs, H. P. Trautvetter and A. E. Vlieks", "title": "Cross section and astrophysical S-factor for the ¹³C(p,γ)¹⁴N reaction", "journal": "Nucl. Phys. A 567, 354 (1994)", "year": 1994, "doi": "10.1016/0375-9474(94)90154-6", "checked": "ScienceDirect record (PII 0375947494901546), OSTI/ETDE record 5009398 and EXFOR entry C0872, by web search, 2026-10-11" }, "gyurky2023": { "key": "gyurky2023", "authors": "Gy. Gyürky, L. Csedreki, T. Szücs, G. G. Kiss, Z. Halász and Zs. Fülöp", "title": "Cross section measurement of the ¹²C(p,γ)¹³N reaction with activation in a wide energy range", "journal": "Eur. Phys. J. A 59, 59 (2023)", "year": 2023, "doi": "10.1140/epja/s10050-023-00974-0", "arxiv": "2303.05999", "checked": "arXiv 2303.05999, Atomki Tandetron news page and EXFOR entry D4426, by web search, 2026-10-11" }, "skowronski2023b": { "key": "skowronski2023b", "authors": "J. Skowronski et al.", "title": "Improved S factor of the ¹²C(p,γ)¹³N reaction at E = 320–620 keV and the 422 keV resonance", "journal": "Phys. Rev. C 107, L062801 (2023)", "year": 2023, "doi": "10.1103/PhysRevC.107.L062801", "arxiv": "2306.09022", "checked": "arXiv 2306.09022, HZDR record Publ-36857 and TU Dresden research portal, by web search, 2026-10-11" }, "kettner2023": { "key": "kettner2023", "authors": "K.-U. Kettner, R. J. deBoer, J. Görres, M. Wiescher et al.", "title": "Absolute cross section of the ¹²C(p,γ)¹³N reaction", "journal": "Phys. Rev. C 108, 035805 (2023)", "year": 2023, "doi": "10.1103/PhysRevC.108.035805", "checked": "OSTI accepted-manuscript record 2419357 (title, authors, journal reference); DOI follows the APS volume and article number, by web search, 2026-10-11" }, "skowronski2023": { "key": "skowronski2023", "authors": "J. Skowronski et al. (LUNA Collaboration)", "title": "Proton-capture rates on carbon isotopes and their impact on the astrophysical ¹²C/¹³C ratio", "journal": "Phys. Rev. Lett. 131, 162701 (2023)", "year": 2023, "doi": "10.1103/PhysRevLett.131.162701", "arxiv": "2308.16098", "luna": true, "checked": "HZDR record Publ-36855, Padova, Milan and Genova IRIS records and JINA Virtual Journal, by web search, 2026-10-11" }, "skowronski2025": { "key": "skowronski2025", "authors": "J. Skowronski, D. Piatti, A. Caciolli, S. Turkat et al.", "title": "Improved S factor of the ¹³C(p,γ)¹⁴N reaction at Ep = 330–740 keV and parameters of resonances at 448 keV and 551 keV", "journal": "Phys. Rev. C 111, 064611 (2025)", "year": 2025, "doi": "10.1103/h1yt-5myk", "arxiv": "2512.17288", "checked": "Milan and Padova IRIS records (journal, DOI), HZDR conference slides and arXiv 2512.17288, by web search; rechecked by search (Milan expertise record, PRC 111(6), 064611, 11 June 2025; S_tot(0) = 6.4(4) keV b in the abstract), 2026-10-11" }, "runkle2005": { "key": "runkle2005", "authors": "R. C. Runkle, A. E. Champagne et al.", "title": "Direct measurement of the ¹⁴N(p,γ)¹⁵O S factor", "journal": "Phys. Rev. Lett. 94, 082503 (2005)", "year": 2005, "doi": "10.1103/PhysRevLett.94.082503", "arxiv": "nucl-ex/0408018", "checked": "arXiv nucl-ex/0408018 (title, journal reference) and EXFOR entry O1195, by web search; DOI from the APS volume and article number, 2026-10-11" }, "imbriani2005": { "key": "imbriani2005", "authors": "G. Imbriani et al. (LUNA Collaboration)", "title": "S-factor of ¹⁴N(p,γ)¹⁵O at astrophysical energies", "journal": "Eur. Phys. J. A 25, 455 (2005)", "year": 2005, "doi": "10.1140/epja/i2005-10138-7", "arxiv": "nucl-ex/0509005", "luna": true, "checked": "abstract (title, journal, energy range 119–367 keV) and Milan AIR record, by web search; DOI and arXiv id (journal reference EPJA 25, 455–466) confirmed by a second web search (EPJA article page, arXiv nucl-ex/0509005), 2026-10-11" }, "bertone2001": { "key": "bertone2001", "authors": "P. F. Bertone, A. E. Champagne, D. C. Powell, C. Iliadis, S. E. Hale and V. Y. Hansper", "title": "Lifetime of the 6793-keV state in ¹⁵O", "journal": "Phys. Rev. Lett. 87, 152501 (2001)", "year": 2001, "doi": "10.1103/PhysRevLett.87.152501", "checked": "INT Seattle archive copy of the article (title, authors, date 8 October 2001), by web search; DOI from the APS volume and article number, 2026-10-11" }, "mukhamedzhanov2003": { "key": "mukhamedzhanov2003", "authors": "A. M. Mukhamedzhanov, P. Bém, B. A. Brown, V. Burjan, C. A. Gagliardi, V. Kroha, J. Novák, F. M. Nunes, Š. Piskoř, F. Pirlepesov, E. Šimečková, R. E. Tribble and J. Vincour", "title": "Asymptotic normalization coefficients for ¹⁴N + p → ¹⁵O and the astrophysical S factor for ¹⁴N(p,γ)¹⁵O", "journal": "Phys. Rev. C 67, 065804 (2003); erratum Phys. Rev. C 68, 019901 (2003)", "year": 2003, "doi": "10.1103/PhysRevC.67.065804", "checked": "INT Seattle archive copy of the article and JINA Virtual Journal listing (with erratum), by web search; DOI from the APS volume and article number, 2026-10-11" }, "wagner2018": { "key": "wagner2018", "authors": "L. Wagner et al.", "title": "Astrophysical S factor of the ¹⁴N(p,γ)¹⁵O reaction at 0.4–1.3 MeV", "journal": "Phys. Rev. C 97, 015801 (2018)", "year": 2018, "doi": "10.1103/PhysRevC.97.015801", "arxiv": "1711.10847", "checked": "HZDR record Publ-25105, TU Dresden research portal and arXiv 1711.10847, by web search; DOI from the APS volume and article number, 2026-10-11" }, "frentz2022": { "key": "frentz2022", "authors": "B. Frentz et al.", "title": "Investigation of the ¹⁴N(p,γ)¹⁵O reaction and its impact on the CNO cycle", "journal": "Phys. Rev. C 106, 065803 (2022)", "year": 2022, "doi": "10.1103/PhysRevC.106.065803", "checked": "APS accepted-manuscript link (DOI) and NSF PAR record, by web search, 2026-10-11" }, "redder1982": { "key": "redder1982", "authors": "A. Redder, H. W. Becker, H. Lorenz-Wirzba, C. Rolfs, P. Schmalbrock and H. P. Trautvetter", "title": "The ¹⁵N(p,α₀)¹²C reaction at stellar energies", "journal": "Z. Phys. A 305, 325 (1982)", "year": 1982, "checked": "EXFOR entry A0142 (authors, journal reference, title given there as \"...reaction of stellar energies\") and citations in Solar Fusion II, by web search; DOI not seen, 2026-10-11" }, "lacognata2007": { "key": "lacognata2007", "authors": "M. La Cognata, S. Romano, C. Spitaleri et al.", "title": "Astrophysical S(E) factor of the ¹⁵N(p,α)¹²C reaction at sub-Coulomb energies via the Trojan horse method", "journal": "Phys. Rev. C 76, 065804 (2007)", "year": 2007, "doi": "10.1103/PhysRevC.76.065804", "checked": "Texas A&M OAKTrust copy (PhysRevC.76.065804) and Catania IRIS record, by web search; DOI from the APS volume and article number, 2026-10-11" }, "lacognata2009": { "key": "lacognata2009", "authors": "M. La Cognata, V. Z. Goldberg, A. M. Mukhamedzhanov, C. Spitaleri and R. E. Tribble", "title": "Improved determination of the astrophysical S(0) factor of the ¹⁵N(p,α)¹²C reaction", "journal": "Phys. Rev. C 80, 012801(R) (2009)", "year": 2009, "doi": "10.1103/PhysRevC.80.012801", "checked": "Texas A&M OAKTrust copy (PhysRevC.80.012801) and JINA Virtual Journal listing, by web search; DOI from the APS volume and article number, 2026-10-11" }, "bemmerer2009": { "key": "bemmerer2009", "authors": "D. Bemmerer et al. (LUNA Collaboration)", "title": "Direct measurement of the ¹⁵N(p,γ)¹⁶O total cross section at novae energies", "journal": "J. Phys. G 36, 045202 (2009)", "year": 2009, "doi": "10.1088/0954-3899/36/4/045202", "arxiv": "0902.0783", "luna": true, "checked": "arXiv 0902.0783 and journal reference cited in later papers, by web search; DOI confirmed by a second web search (arXiv journal-ref, HZDR Publ-12340, Milan AIR), 2026-10-11" }, "mukhamedzhanov2008": { "key": "mukhamedzhanov2008", "authors": "A. M. Mukhamedzhanov et al.", "title": "New astrophysical S factor for the ¹⁵N(p,γ)¹⁶O reaction via the asymptotic normalization coefficient (ANC) method", "journal": "Phys. Rev. C 78, 015804 (2008)", "year": 2008, "doi": "10.1103/PhysRevC.78.015804", "checked": "Texas A&M OAKTrust copy (PhysRevC.78.015804) and Czech Academy ASEP record (title truncated after \"coeff...\"), by web search; DOI from the APS volume and article number, 2026-10-11" }, "leblanc2010": { "key": "leblanc2010", "authors": "P. J. LeBlanc, G. Imbriani, J. Görres, M. Wiescher et al.", "title": "Constraining the S factor of ¹⁵N(p,γ)¹⁶O at astrophysical energies", "journal": "Phys. Rev. C 82, 055804 (2010)", "year": 2010, "doi": "10.1103/PhysRevC.82.055804", "arxiv": "1011.2518", "checked": "arXiv 1011.2518, HZDR record Publ-14900 and Milan AIR record (DOI), by web search, 2026-10-11" }, "caciolli2011": { "key": "caciolli2011", "authors": "A. Caciolli et al. (LUNA Collaboration)", "title": "Revision of the ¹⁵N(p,γ)¹⁶O reaction rate and oxygen abundance in H-burning zones", "journal": "Astron. Astrophys. 533, A66 (2011)", "year": 2011, "doi": "10.1051/0004-6361/201117475", "arxiv": "1107.4514", "luna": true, "checked": "arXiv 1107.4514 and A&A DOI page, by web search, 2026-10-11" }, "imbriani2012": { "key": "imbriani2012", "authors": "G. Imbriani, R. J. deBoer, A. Best, M. Couder, G. Gervino, J. Görres, P. J. LeBlanc, H. Leiste, A. Lemut, E. Stech, F. Strieder, E. Uberseder and M. Wiescher", "title": "Measurement of γ rays from ¹⁵N(p,γ)¹⁶O cascade and ¹⁵N(p,α₁γ)¹²C reactions", "journal": "Phys. Rev. C 85, 065810 (2012); erratum Phys. Rev. C 86, 039902 (2012)", "year": 2012, "doi": "10.1103/PhysRevC.85.065810", "checked": "APS accepted-manuscript link (DOI) and Naples IRIS record, by web search, 2026-10-11" }, "morlock1997": { "key": "morlock1997", "authors": "R. Morlock, R. Kunz, A. Mayer, M. Jaeger et al.", "title": "Halo properties of the first 1/2⁺ state in ¹⁷F from the ¹⁶O(p,γ)¹⁷F reaction", "journal": "Phys. Rev. Lett. 79, 3837 (1997)", "year": 1997, "doi": "10.1103/PhysRevLett.79.3837", "checked": "title from the published Comment (arXiv nucl-ex/9712007) and citation in Solar Fusion II, by web search; DOI from the APS volume and article number; full author list not seen, 2026-10-11" }, "iliadis2008": { "key": "iliadis2008", "authors": "C. Iliadis, C. Angulo, P. Descouvemont, M. Lugaro and P. Mohr", "title": "New reaction rate for ¹⁶O(p,γ)¹⁷F and its influence on the oxygen isotopic ratios in massive AGB stars", "journal": "Phys. Rev. C 77, 045802 (2008)", "year": 2008, "doi": "10.1103/PhysRevC.77.045802", "arxiv": "0803.2757", "checked": "arXiv 0803.2757 and JINA Virtual Journal listing, by web search; DOI from the APS volume and article number, 2026-10-11" }, "sergi2010": { "key": "sergi2010", "authors": "M. L. Sergi, C. Spitaleri, M. La Cognata et al.", "title": "New high accuracy measurement of the ¹⁷O(p,α)¹⁴N reaction rate at astrophysical temperatures", "journal": "Phys. Rev. C 82, 032801(R) (2010)", "year": 2010, "doi": "10.1103/PhysRevC.82.032801", "checked": "Czech Academy ASEP record 0348012 and Catania IRIS record, by web search; DOI from the APS volume and article number, 2026-10-11" }, "sergi2015": { "key": "sergi2015", "authors": "M. L. Sergi, C. Spitaleri, M. La Cognata et al.", "title": "Improvement of the high-accuracy ¹⁷O(p,α)¹⁴N reaction-rate measurement via the Trojan Horse method for application to ¹⁷O nucleosynthesis", "journal": "Phys. Rev. C 91, 065803 (2015)", "year": 2015, "doi": "10.1103/PhysRevC.91.065803", "checked": "Czech Academy ASEP record 0445860 and APS accepted-manuscript link (DOI), by web search, 2026-10-11" }, "chafa2005": { "key": "chafa2005", "authors": "A. Chafa, V. Tatischeff et al.", "title": "Hydrogen burning of ¹⁷O in classical novae", "journal": "Phys. Rev. Lett. 95, 031101 (2005)", "year": 2005, "doi": "10.1103/PhysRevLett.95.031101", "arxiv": "astro-ph/0506500", "checked": "arXiv astro-ph/0506500 and HAL record in2p3-00024492, by web search; DOI from the APS volume and article number, 2026-10-11" }, "moazen2007": { "key": "moazen2007", "authors": "B. H. Moazen et al.", "title": "Measurement of the 183 keV resonance in ¹⁷O(p,α)¹⁴N using a novel technique", "journal": "Phys. Rev. C 75, 065801 (2007)", "year": 2007, "doi": "10.1103/PhysRevC.75.065801", "checked": "LSU and ORNL publication records and EXFOR entry C1567 (HRIBF, Oak Ridge), by web search; DOI from the APS volume and article number, 2026-10-11" }, "bruno2015": { "key": "bruno2015", "authors": "C. G. Bruno et al. (LUNA Collaboration)", "title": "Resonance strengths in the ¹⁷,¹⁸O(p,α)¹⁴,¹⁵N reactions and background suppression underground", "journal": "Eur. Phys. J. A 51, 94 (2015)", "year": 2015, "doi": "10.1140/epja/i2015-15094-y", "luna": true, "checked": "EPJ A abstract page, HZDR record Publ-22410 and Milan AIR record, by web search, 2026-10-11" }, "bruno2016": { "key": "bruno2016", "authors": "C. G. Bruno et al. (LUNA Collaboration)", "title": "Improved direct measurement of the 64.5 keV resonance strength in the ¹⁷O(p,α)¹⁴N reaction at LUNA", "journal": "Phys. Rev. Lett. 117, 142502 (2016)", "year": 2016, "doi": "10.1103/PhysRevLett.117.142502", "arxiv": "1610.00483", "luna": true, "checked": "arXiv 1610.00483, HZDR record Publ-24057 and JINA Virtual Journal listing, by web search, 2026-10-11" }, "fox2005": { "key": "fox2005", "authors": "C. Fox, C. Iliadis, A. E. Champagne, R. P. Fitzgerald, R. Longland, J. Newton, J. Pollanen and R. Runkle", "title": "Thermonuclear reaction rate of ¹⁷O(p,γ)¹⁸F", "journal": "Phys. Rev. C 71, 055801 (2005)", "year": 2005, "doi": "10.1103/PhysRevC.71.055801", "checked": "EXFOR entry C1259 (authors, LENA, Ep = 140–540 keV) and JINA Virtual Journal listing, by web search; DOI from the APS volume and article number, 2026-10-11" }, "hager2012": { "key": "hager2012", "authors": "U. Hager et al.", "title": "Measurement of the ¹⁷O(p,γ)¹⁸F reaction rate at astrophysically relevant energies", "journal": "Phys. Rev. C 85, 035803 (2012)", "year": 2012, "doi": "10.1103/PhysRevC.85.035803", "checked": "APS accepted-manuscript link (DOI) and Caltech/IPAC ADS record, by web search, 2026-10-11" }, "kontos2012": { "key": "kontos2012", "authors": "A. Kontos, J. Görres, A. Best, M. Couder, R. deBoer, G. Imbriani, Q. Li, D. Robertson, D. Schürmann, E. Stech, E. Uberseder and M. Wiescher", "title": "Proton capture on ¹⁷O and its astrophysical implications", "journal": "Phys. Rev. C 86, 055801 (2012); erratum Phys. Rev. C 88, 029905 (2013)", "year": 2012, "doi": "10.1103/PhysRevC.86.055801", "arxiv": "1210.7866", "checked": "arXiv 1210.7866, APS accepted-manuscript link (DOI) and JINA Virtual Journal listing, by web search, 2026-10-11" }, "scott2012": { "key": "scott2012", "authors": "D. A. Scott et al. (LUNA Collaboration)", "title": "First direct measurement of the ¹⁷O(p,γ)¹⁸F reaction cross section at Gamow energies for classical novae", "journal": "Phys. Rev. Lett. 109, 202501 (2012)", "year": 2012, "doi": "10.1103/PhysRevLett.109.202501", "arxiv": "1210.6529", "luna": true, "checked": "arXiv 1210.6529 and Milan, Naples, Turin and Padova IRIS records, by web search, 2026-10-11" }, "dileva2014": { "key": "dileva2014", "authors": "A. Di Leva et al. (LUNA Collaboration)", "title": "Underground study of the ¹⁷O(p,γ)¹⁸F reaction relevant for explosive hydrogen burning", "journal": "Phys. Rev. C 89, 015803 (2014)", "year": 2014, "doi": "10.1103/PhysRevC.89.015803", "luna": true, "checked": "HZDR record Publ-19863 and Turin and Milan IRIS records (an erratum is also listed), by web search; DOI from the APS volume and article number, 2026-10-11" }, "buckner2015": { "key": "buckner2015", "authors": "M. Q. Buckner, C. Iliadis, K. J. Kelly, L. N. Downen, A. E. Champagne, J. M. Cesaratto, C. Howard and R. Longland", "title": "High-intensity-beam study of ¹⁷O(p,γ)¹⁸F and thermonuclear reaction rates for ¹⁷O + p", "journal": "Phys. Rev. C 91, 015812 (2015)", "year": 2015, "doi": "10.1103/PhysRevC.91.015812", "checked": "APS accepted-manuscript link (DOI) and EXFOR entry C2155, by web search, 2026-10-11" }, "gesue2024": { "key": "gesue2024", "authors": "R. M. Gesuè et al. (LUNA Collaboration)", "title": "First direct measurement of the 64.5 keV resonance strength in the ¹⁷O(p,γ)¹⁸F reaction", "journal": "Phys. Rev. Lett. 133, 052701 (2024)", "year": 2024, "doi": "10.1103/PhysRevLett.133.052701", "arxiv": "2408.03015", "luna": true, "checked": "arXiv 2408.03015 and Padova, Genova and Naples IRIS records, by web search; DOI from the APS volume and article number, 2026-10-11" }, "buckner2012": { "key": "buckner2012", "authors": "M. Q. Buckner, C. Iliadis et al.", "title": "Thermonuclear reaction rate of ¹⁸O(p,γ)¹⁹F", "journal": "Phys. Rev. C 86, 065804 (2012)", "year": 2012, "doi": "10.1103/PhysRevC.86.065804", "arxiv": "1212.1126", "checked": "arXiv 1212.1126 and EXFOR entry C1964 (LENA), by web search; DOI from the APS volume and article number, 2026-10-11" }, "best2019": { "key": "best2019", "authors": "A. Best et al. (LUNA Collaboration)", "title": "Cross section of the reaction ¹⁸O(p,γ)¹⁹F at astrophysical energies: the 90 keV resonance and the direct capture component", "journal": "Phys. Lett. B 797, 134900 (2019)", "year": 2019, "doi": "10.1016/j.physletb.2019.134900", "luna": true, "checked": "HZDR record Publ-29655, Naples and Milan IRIS records and library DOI record, by web search, 2026-10-11" }, "pantaleo2021": { "key": "pantaleo2021", "authors": "F. R. Pantaleo et al. (LUNA Collaboration)", "title": "Low-energy cross section of the ¹⁸O(p,γ)¹⁹F reaction", "journal": "Phys. Rev. C 104, 025802 (2021)", "year": 2021, "doi": "10.1103/PhysRevC.104.025802", "luna": true, "checked": "Bari IRIS full-text file and Padova repository copy (PhysRevC.104.025802), by web search; exact title wording taken from the repository file name; DOI from the APS volume and article number, 2026-10-11" }, "lacognata2008": { "key": "lacognata2008", "authors": "M. La Cognata, C. Spitaleri et al.", "title": "Measurement of the 20 and 90 keV resonances in the ¹⁸O(p,α)¹⁵N reaction via the Trojan Horse method", "journal": "Phys. Rev. Lett. 101, 152501 (2008)", "year": 2008, "doi": "10.1103/PhysRevLett.101.152501", "arxiv": "0806.1274", "checked": "arXiv 0806.1274 and INT Seattle archive copy (published 7 October 2008), by web search; volume and article number not shown by those sources; DOI from the APS volume and article number, 2026-10-11" }, "bruno2019": { "key": "bruno2019", "authors": "C. G. Bruno et al. (LUNA Collaboration)", "title": "Improved astrophysical rate for the ¹⁸O(p,α)¹⁵N reaction by underground measurements", "journal": "Phys. Lett. B 790, 237 (2019)", "year": 2019, "doi": "10.1016/j.physletb.2019.01.017", "luna": true, "checked": "DOAJ record (Phys. Lett. B, March 2019) and LUNA reference list (PLB 790, 237–242), by web search; DOI from the SCOAP3 open-access copy and HZDR Publ-28791, found by a second search, 2026-10-11" }, "couture2008": { "key": "couture2008", "authors": "A. Couture, M. Wiescher et al.", "title": "Measurement of the ¹⁹F(p,γ)²⁰Ne reaction and interference terms from E(c.m.) = 200–760 keV", "journal": "Phys. Rev. C 77, 015802 (2008)", "year": 2008, "doi": "10.1103/PhysRevC.77.015802", "checked": "JINA Virtual Journal listing (title, volume, article) and Solar Fusion III (arXiv 2405.06470), by web search; DOI from the APS volume and article number, 2026-10-11" }, "zhang2021": { "key": "zhang2021", "authors": "L. Y. Zhang et al. (JUNA Collaboration)", "title": "Direct measurement of the astrophysical ¹⁹F(p,αγ)¹⁶O reaction in the deepest operational underground laboratory", "journal": "Phys. Rev. Lett. 127, 152702 (2021)", "year": 2021, "doi": "10.1103/PhysRevLett.127.152702", "checked": "JINA Virtual Journal listing (DOI) and NSF PAR record, by web search, 2026-10-11" }, "lacognata2011": { "key": "lacognata2011", "authors": "M. La Cognata et al.", "title": "The fluorine destruction in stars: first experimental study of the ¹⁹F(p,α₀)¹⁶O reaction at astrophysical energies", "journal": "Astrophys. J. Lett. 739, L54 (2011)", "year": 2011, "doi": "10.1088/2041-8205/739/2/L54", "checked": "DOI link and Catania IRIS record (journal, abstract); title confirmed by the Atomki APHA author database and the TAMU abstract citation, 2026-10-11" }, "lombardo2015": { "key": "lombardo2015", "authors": "I. Lombardo, D. Dell'Aquila, A. Di Leva, I. Indelicato et al.", "title": "Toward a reassessment of the ¹⁹F(p,α₀)¹⁶O reaction rate at astrophysical temperatures", "journal": "Phys. Lett. B 748, 178 (2015)", "year": 2015, "checked": "DOAJ record and Naples IRIS record, by web search; DOI not seen, 2026-10-11" }, "indelicato2017": { "key": "indelicato2017", "authors": "I. Indelicato et al.", "title": "New improved indirect measurement of the ¹⁹F(p,α)¹⁶O reaction at energies of astrophysical relevance", "journal": "Astrophys. J. 845, 19 (2017)", "year": 2017, "checked": "Padova repository copy (Indelicato_2017_ApJ_845_19.pdf) and Sassari IRIS record, by web search; DOI not seen, 2026-10-11" }, "schurmann2008": { "key": "schurmann2008", "authors": "D. Schürmann et al.", "title": "Lifetime measurement of the 6792 keV state in ¹⁵O, important for the astrophysical S factor extrapolation in ¹⁴N(p,γ)¹⁵O", "journal": "Phys. Rev. C 77, 055803 (2008)", "year": 2008, "doi": "10.1103/PhysRevC.77.055803", "arxiv": "0804.1934", "checked": "arXiv 0804.1934 (abstract, τ < 0.77 fs) and JINA Virtual Journal listing (PRC 77, issue 5, 055803), by web search; DOI from the APS volume and article number, 2026-10-11" }, "frentz2021": { "key": "frentz2021", "authors": "B. Frentz et al.", "title": "Lifetime measurements of excited states in ¹⁵O", "journal": "Phys. Rev. C 103, 045802 (2021)", "year": 2021, "doi": "10.1103/PhysRevC.103.045802", "checked": "APS accepted-manuscript page for the DOI and NSF PAR copy (published 7 April 2021; τ = 0.6 ± 0.4 fs for the 6792 keV state), by web search, 2026-10-11" }, "gyurky2022": { "key": "gyurky2022", "authors": "Gy. Gyürky, Z. Halász, G. G. Kiss, T. Szücs, Zs. Fülöp", "title": "Activation cross section measurement of the ¹⁴N(p,γ)¹⁵O astrophysical key reaction", "journal": "Phys. Rev. C 105, L022801 (2022)", "year": 2022, "doi": "10.1103/PhysRevC.105.L022801", "arxiv": "2201.10176", "checked": "arXiv 2201.10176 and Atomki Tandetron news page (journal reference, DOI, 550–1400 keV, about 10 % uncertainty), by web search, 2026-10-11" }, "gosta2025": { "key": "gosta2025", "authors": "G. Gosta et al. (LUNA Collaboration)", "title": "The SOCIAL project: measurement of the ¹⁴N(p,γ)¹⁵O cross section", "journal": "Eur. Phys. J. A 61, 110 (2025)", "year": 2025, "doi": "10.1140/epja/s10050-025-01561-1", "luna": true, "checked": "ADS record 2025EPJA...61..110G, EPJA abstract page and Milan expertise record (May 2025), by web search; full author list not seen, 2026-10-11" }, "compagnucci2025": { "key": "compagnucci2025", "authors": "A. Compagnucci et al. (LUNA Collaboration)", "title": "Towards a comprehensive study of the ¹⁴N(p,γ)¹⁵O astrophysical key reaction: description of the experimental technique including novel target preparation", "journal": "Eur. Phys. J. A 61, 191 (2025)", "year": 2025, "doi": "10.1140/epja/s10050-025-01658-7", "luna": true, "checked": "author's publication list (content/publications.yaml); a 2025 conference abstract by A. Compagnucci on the same campaign found by search, 2026-10-11" }, "adelberger2011": { "key": "adelberger2011", "authors": "E. G. Adelberger et al.", "title": "Solar fusion cross sections II: the pp chain and CNO cycles", "journal": "Rev. Mod. Phys. 83, 195 (2011)", "year": 2011, "doi": "10.1103/RevModPhys.83.195", "checked": "publisher DOI confirmed by search (HZDR and Surrey repository records), 2026-10-11" }, "acharya2025": { "key": "acharya2025", "authors": "B. Acharya et al.", "title": "Solar fusion III: New data and theory for hydrogen-burning stars", "journal": "Rev. Mod. Phys. 97, 035002 (2025)", "year": 2025, "doi": "10.1103/8lm7-gs18", "arxiv": "2405.06470", "checked": "arXiv 2405.06470 and DOI from the JINA Virtual Journal and Milan IRIS records, 2026-10-11" }, "borexino2020": { "key": "borexino2020", "authors": "Borexino Collaboration", "title": "Experimental evidence of neutrinos produced in the CNO fusion cycle in the Sun", "journal": "Nature 587, 577 (2020)", "year": 2020, "doi": "10.1038/s41586-020-2934-0", "checked": "PubMed record 33239797, 2026-10-11" }, "angulo1999": { "key": "angulo1999", "authors": "C. Angulo, M. Arnould, M. Rayet et al. (NACRE Collaboration)", "title": "A compilation of charged-particle induced thermonuclear reaction rates", "journal": "Nucl. Phys. A 656, 3 (1999)", "year": 1999, "checked": "journal, volume and pages from the INSPIRE record 522312 and citing reference lists; DOI not shown by any record found, so omitted, 2026-10-11" }, "xu2013": { "key": "xu2013", "authors": "Y. Xu, K. Takahashi, S. Goriely, M. Arnould, M. Ohta, H. Utsunomiya", "title": "NACRE II: an update of the NACRE compilation of charged-particle-induced thermonuclear reaction rates for nuclei with mass number A < 16", "journal": "Nucl. Phys. A 918, 61 (2013)", "year": 2013, "doi": "10.1016/j.nuclphysa.2013.09.007", "arxiv": "1310.7099", "checked": "arXiv 1310.7099 listing and GSI repository record giving the DOI, 2026-10-11" }, "deboer2017": { "key": "deboer2017", "authors": "R. J. deBoer, J. Görres, M. Wiescher, R. E. Azuma, A. Best, C. R. Brune, C. E. Fields, S. Jones, M. Pignatari, D. Sayre, K. Smith, F. X. Timmes, E. Uberseder", "title": "The ¹²C(α,γ)¹⁶O reaction and its implications for stellar helium burning", "journal": "Rev. Mod. Phys. 89, 035007 (2017)", "year": 2017, "doi": "10.1103/RevModPhys.89.035007", "arxiv": "1709.03144", "checked": "Hull repository record (authors, DOI), NSF PAR copy and arXiv 1709.03144, 2026-10-11" }, "freer2014": { "key": "freer2014", "authors": "M. Freer, H. O. U. Fynbo", "title": "The Hoyle state in ¹²C", "journal": "Prog. Part. Nucl. Phys. 78, 1 (2014)", "year": 2014, "doi": "10.1016/j.ppnp.2014.06.001", "checked": "University of Birmingham repository record and accepted manuscript, 2026-10-11" }, "adsley2021": { "key": "adsley2021", "authors": "P. Adsley et al.", "title": "Reevaluation of the ²²Ne(α,γ)²⁶Mg and ²²Ne(α,n)²⁵Mg reaction rates", "journal": "Phys. Rev. C 103, 015805 (2021)", "year": 2021, "doi": "10.1103/PhysRevC.103.015805", "arxiv": "2005.14482", "checked": "arXiv 2005.14482, Keele repository record and JINA Virtual Journal listing, 2026-10-11" }, "fynbo2005": { "key": "fynbo2005", "authors": "H. O. U. Fynbo, C. Aa. Diget, U. C. Bergmann et al.", "title": "Revised rates for the stellar triple-α process from measurement of ¹²C nuclear resonances", "journal": "Nature 433, 136 (2005)", "year": 2005, "doi": "10.1038/nature03219", "checked": "Chalmers research record and RePEc listing (DOI, pages 136–139), 2026-10-11" }, "eriksen2020": { "key": "eriksen2020", "authors": "T. K. Eriksen, T. Kibédi, M. W. Reed et al.", "title": "Improved precision on the experimental E0 decay branching ratio of the Hoyle state", "journal": "Phys. Rev. C 102, 024320 (2020)", "year": 2020, "doi": "10.1103/PhysRevC.102.024320", "arxiv": "2007.15374", "checked": "arXiv 2007.15374 and Bangor and ANU repository records (journal, volume, article number); DOI by APS scheme from the confirmed journal reference, 2026-10-11" }, "kibedi2020": { "key": "kibedi2020", "authors": "T. Kibédi et al.", "title": "Radiative width of the Hoyle state from γ-ray spectroscopy", "journal": "Phys. Rev. Lett. 125, 182701 (2020)", "year": 2020, "doi": "10.1103/PhysRevLett.125.182701", "arxiv": "2009.10915", "checked": "arXiv 2009.10915, APS accepted-manuscript page and University of Oslo repository copy, 2026-10-11" }, "tsumura2021": { "key": "tsumura2021", "authors": "M. Tsumura et al.", "title": "First experimental determination of the radiative-decay probability of the 3⁻₁ state in ¹²C for estimating the triple alpha reaction rate in high temperature environments", "journal": "Phys. Lett. B 817, 136283 (2021)", "year": 2021, "doi": "10.1016/j.physletb.2021.136283", "checked": "INSPIRE full-text mirror, Kyoto University repository and DOAJ listing (journal, DOI); full title as searched, not displayed verbatim by a record, 2026-10-11" }, "paulsen2025": { "key": "paulsen2025", "authors": "W. Paulsen et al.", "title": "Remeasuring the γ-decay branching ratio of the Hoyle state", "journal": "Phys. Rev. C 112, 015803 (2025)", "year": 2025, "doi": "10.1103/2h2s-sbyx", "arxiv": "2406.00397", "checked": "APS abstract page for the DOI (volume, article number, 2 July 2025) and arXiv 2406.00397 (v2 retitled \"A saga on the γ-decay branching ratio of the Hoyle state\"), 2026-10-11; results rechecked by web search (Γγ/Γ = 4.0(3) × 10⁻⁴, Γrad/Γ = 4.1(4) × 10⁻⁴; reanalysis of the Kibédi et al. data gives 4.6(6) × 10⁻⁴, no longer discrepant with the ENSDF average 4.16(11) × 10⁻⁴), 2026-10-13" }, "kunz2001": { "key": "kunz2001", "authors": "R. Kunz, M. Jaeger, A. Mayer, J. W. Hammer, G. Staudt, S. Harissopulos, T. Paradellis", "title": "¹²C(α,γ)¹⁶O: the key reaction in stellar nucleosynthesis", "journal": "Phys. Rev. Lett. 86, 3244 (2001)", "year": 2001, "doi": "10.1103/PhysRevLett.86.3244", "checked": "IAEA EXFOR entry A0428 (authors, journal reference and DOI) found by search, 2026-10-11" }, "kunz2002": { "key": "kunz2002", "authors": "R. Kunz, M. Jaeger, A. Mayer, J. W. Hammer, G. Staudt, S. Harissopulos, T. Paradellis", "title": "Astrophysical reaction rate of ¹²C(α,γ)¹⁶O", "journal": "Astrophys. J. 567, 643 (2002)", "year": 2002, "doi": "10.1086/338384", "checked": "IAEA EXFOR entry A0428 (reference and DOI) and citing papers, 2026-10-11" }, "hammer2005": { "key": "hammer2005", "authors": "J. W. Hammer, M. Fey, R. Kunz et al.", "title": "E1 and E2 capture cross section and astrophysical reaction rate of the key reaction ¹²C(α,γ)¹⁶O", "journal": "Nucl. Phys. A 758, 363 (2005)", "year": 2005, "doi": "10.1016/j.nuclphysa.2005.05.066", "checked": "IAC publication record (pages 363–366) and Academic Search Index record giving the DOI, 2026-10-11" }, "schurmann2005": { "key": "schurmann2005", "authors": "D. Schürmann et al.", "title": "First direct measurement of the total cross-section of ¹²C(α,γ)¹⁶O", "journal": "Eur. Phys. J. A 26, 301 (2005)", "year": 2005, "doi": "10.1140/epja/i2005-10175-2", "arxiv": "nucl-ex/0511050", "checked": "arXiv nucl-ex/0511050 and EPJ A article page, 2026-10-11" }, "assuncao2006": { "key": "assuncao2006", "authors": "M. Assunção et al.", "title": "E1 and E2 S factors of ¹²C(α,γ₀)¹⁶O from γ-ray angular distributions with a 4π-detector array", "journal": "Phys. Rev. C 73, 055801 (2006)", "year": 2006, "doi": "10.1103/PhysRevC.73.055801", "checked": "HAL in2p3-00067806, JINA Virtual Journal listing and IAEA EXFOR O1420, 2026-10-11" }, "matei2006": { "key": "matei2006", "authors": "C. Matei, L. Buchmann, W. R. Hannes, D. A. Hutcheon, C. Ruiz, C. R. Brune, J. Caggiano, A. A. Chen, J. D'Auria, A. Laird et al.", "title": "Measurement of the cascade transition via the first excited state of ¹⁶O in the ¹²C(α,γ)¹⁶O reaction, and its S factor in stellar helium burning", "journal": "Phys. Rev. Lett. 97, 242503 (2006)", "year": 2006, "doi": "10.1103/PhysRevLett.97.242503", "checked": "McMaster experts record and INIS record (authors, DOI, abstract); title from memory, consistent with the abstract, 2026-10-11" }, "schurmann2011": { "key": "schurmann2011", "authors": "D. Schürmann, A. Di Leva, L. Gialanella, R. Kunz, F. Strieder et al.", "title": "Study of the 6.05 MeV cascade transition in ¹²C(α,γ)¹⁶O", "journal": "Phys. Lett. B 703, 557 (2011)", "year": 2011, "doi": "10.1016/j.physletb.2011.08.061", "checked": "University of Naples and University of Campania IRIS records (authors, pages, DOI) and IAEA EXFOR O1957, 2026-10-11" }, "plag2012": { "key": "plag2012", "authors": "R. Plag, R. Reifarth, M. Heil, F. Käppeler, G. Rupp, F. Voss, K. Wisshak", "title": "¹²C(α,γ)¹⁶O studied with the Karlsruhe 4π BaF₂ detector", "journal": "Phys. Rev. C 86, 015805 (2012)", "year": 2012, "doi": "10.1103/PhysRevC.86.015805", "checked": "GSI repository record GSI-2013-05617, IAEA EXFOR O1988 and author copy at usc.gal, 2026-10-11" }, "costantini2010": { "key": "costantini2010", "authors": "H. Costantini, R. J. deBoer, R. E. Azuma, M. Couder, J. Görres, J. W. Hammer et al.", "title": "¹⁶O(α,γ)²⁰Ne S factor: measurements and R-matrix analysis", "journal": "Phys. Rev. C 82, 035802 (2010)", "year": 2010, "doi": "10.1103/PhysRevC.82.035802", "checked": "ANU and Surrey repository records (journal, article number, DOI) and JINA Virtual Journal listing, 2026-10-11" }, "hager2011": { "key": "hager2011", "authors": "U. Hager, J. R. Brown, L. Buchmann et al.", "title": "Direct total cross section measurement of the ¹⁶O(α,γ)²⁰Ne reaction at E(c.m.) = 2.26 MeV", "journal": "Phys. Rev. C 84, 022801 (2011)", "year": 2011, "doi": "10.1103/PhysRevC.84.022801", "checked": "PNNL publication record (authors, DOI, abstract) and IAEA EXFOR C1854, 2026-10-11" }, "gorres2000": { "key": "gorres2000", "authors": "J. Görres, C. Arlandini, U. Giesen, M. Heil, F. Käppeler, H. Leiste, E. Stech, M. Wiescher", "title": "Low-energy resonances in ¹⁴N(α,γ)¹⁸F and their astrophysical implications", "journal": "Phys. Rev. C 62, 055801 (2000)", "year": 2000, "doi": "10.1103/PhysRevC.62.055801", "checked": "IAEA EXFOR entry C0843 (authors, title, facilities at Karlsruhe and Notre Dame) and KIT library record found by search; DOI by APS scheme, 2026-10-11" }, "dababneh2003": { "key": "dababneh2003", "authors": "S. Dababneh et al.", "title": "Stellar He burning of ¹⁸O: a measurement of low-energy resonances and their astrophysical implications", "journal": "Phys. Rev. C 68, 025801 (2003)", "year": 2003, "doi": "10.1103/PhysRevC.68.025801", "checked": "INIS record (title, abstract, Karlsruhe, Los Alamos and Notre Dame affiliations) and the Karlsruhe dissertation FZKA 6782 found by search; journal reference as cited, DOI by APS scheme, 2026-10-11" }, "dombos2022": { "key": "dombos2022", "authors": "A. C. Dombos et al.", "title": "Measurement of low-energy resonance strengths in the ¹⁸O(α,γ)²²Ne reaction", "journal": "Phys. Rev. Lett. 128, 162701 (2022)", "year": 2022, "doi": "10.1103/PhysRevLett.128.162701", "checked": "APS accepted-manuscript page for the DOI, NSF PAR copy and Sanford Lab publication page (abstract) found by search, 2026-10-11" }, "best2013": { "key": "best2013", "authors": "A. Best, M. Beard et al.", "title": "Measurement of the reaction ¹⁷O(α,n)²⁰Ne and its impact on the s process in massive stars", "journal": "Phys. Rev. C 87, 045805 (2013)", "year": 2013, "doi": "10.1103/PhysRevC.87.045805", "arxiv": "1304.6443", "checked": "Hull repository record, JINA Virtual Journal listing and published PDF hosted at usc.gal found by search; DOI by APS scheme, 2026-10-11" }, "williams2022": { "key": "williams2022", "authors": "M. Williams, A. M. Laird, A. Choplin, P. Adsley, B. Davids, U. Greife, K. Hudson, D. Hutcheon, A. Lennarz, C. Ruiz", "title": "Constraints on key ¹⁷O(α,γ)²¹Ne resonances and impact on the weak s-process", "journal": "Phys. Rev. C 105, 065805 (2022)", "year": 2022, "doi": "10.1103/PhysRevC.105.065805", "arxiv": "2206.06016", "checked": "arXiv 2206.06016 and ULB repository record (journal, DOI) found by search, 2026-10-11" }, "drotleff1993": { "key": "drotleff1993", "authors": "H. W. Drotleff, A. Denker, H. Knee, M. Soiné, G. Wolf, J. W. Hammer, U. Greife, C. Rolfs, H. P. Trautvetter", "title": "Reaction rates of the s-process neutron sources ¹³C(α,n)¹⁶O and ²²Ne(α,n)²⁵Mg", "journal": "Astrophys. J. 414, 735 (1993)", "year": 1993, "checked": "full citation in the reference list of arXiv 0810.1262 (Ugalde, review of ²²Ne(α,n)²⁵Mg); DOI not confirmed, so omitted, 2026-10-11" }, "heil2008": { "key": "heil2008", "authors": "M. Heil et al.", "title": "The ¹³C(α,n) reaction and its role as a neutron source for the s process", "journal": "Phys. Rev. C 78, 025803 (2008)", "year": 2008, "doi": "10.1103/PhysRevC.78.025803", "checked": "KIT library record (DOI) and JINA Virtual Journal listing, 2026-10-11" }, "lacognata2012": { "key": "lacognata2012", "authors": "M. La Cognata et al.", "title": "Measurement of the −3 keV resonance in the reaction ¹³C(α,n)¹⁶O of importance in the s-process", "journal": "Phys. Rev. Lett. 109, 232701 (2012)", "year": 2012, "doi": "10.1103/PhysRevLett.109.232701", "checked": "APS accepted-manuscript page for the DOI and Texas A&M Cyclotron Institute publication record, 2026-10-11" }, "avila2015": { "key": "avila2015", "authors": "M. L. Avila et al.", "title": "New α ANC measurement of the 1/2⁺ state in ¹⁷O at 6.356 MeV, that dominates the ¹³C(α,n)¹⁶O reaction rate at temperatures relevant for the s-process", "journal": "Phys. Rev. C 91, 048801 (2015)", "year": 2015, "doi": "10.1103/PhysRevC.91.048801", "arxiv": "1503.08743", "checked": "arXiv 1503.08743 and IAEA EXFOR C2158 (journal reference); DOI by APS scheme from the confirmed journal reference, 2026-10-11" }, "deboer2020": { "key": "deboer2020", "authors": "R. J. deBoer, C. R. Brune, M. Febbraro, J. Görres, I. J. Thompson, M. Wiescher", "title": "Sensitivity of the ¹³C(α,n)¹⁶O S factor to the uncertainty in the level parameters of the near-threshold state", "journal": "Phys. Rev. C 101, 045802 (2020)", "year": 2020, "doi": "10.1103/PhysRevC.101.045802", "checked": "NSF PAR record 10174275 and JINA Virtual Journal listing, 2026-10-11" }, "ciani2021": { "key": "ciani2021", "authors": "G. F. Ciani et al. (LUNA Collaboration)", "title": "Direct measurement of the ¹³C(α,n)¹⁶O cross section into the s-process Gamow peak", "journal": "Phys. Rev. Lett. 127, 152701 (2021)", "year": 2021, "doi": "10.1103/PhysRevLett.127.152701", "arxiv": "2110.00303", "luna": true, "checked": "INAF open-access record (arXiv 2110.00303, DOI, abstract), HZDR repository and University of Genoa copy, 2026-10-11" }, "gao2022": { "key": "gao2022", "authors": "B. Gao, T. Y. Jiao, Y. T. Li et al. (JUNA Collaboration)", "title": "Deep underground laboratory measurement of ¹³C(α,n)¹⁶O in the Gamow windows of the s and i processes", "journal": "Phys. Rev. Lett. 129, 132701 (2022)", "year": 2022, "doi": "10.1103/PhysRevLett.129.132701", "arxiv": "2210.03222", "checked": "arXiv 2210.03222, NSF PAR copy and JINA Virtual Journal listing, 2026-10-11" }, "jaeger2001": { "key": "jaeger2001", "authors": "M. Jaeger, R. Kunz, A. Mayer, J. W. Hammer, G. Staudt, K. L. Kratz, B. Pfeiffer", "title": "²²Ne(α,n)²⁵Mg: the key neutron source in massive stars", "journal": "Phys. Rev. Lett. 87, 202501 (2001)", "year": 2001, "doi": "10.1103/PhysRevLett.87.202501", "checked": "full citation in the reference list of arXiv 0810.1262 and the Stuttgart thesis record of M. Jaeger (Dynamitron, Rhinoceros gas target); DOI by APS scheme from the confirmed journal reference, 2026-10-11" }, "massimi2017": { "key": "massimi2017", "authors": "C. Massimi et al. (n_TOF Collaboration)", "title": "Neutron spectroscopy of ²⁶Mg states: constraining the stellar neutron source ²²Ne(α,n)²⁵Mg", "journal": "Phys. Lett. B 768, 1 (2017)", "year": 2017, "doi": "10.1016/j.physletb.2017.02.025", "arxiv": "1702.04520", "checked": "University of Hertfordshire and JRC repository records (pages 1–6, DOI) and arXiv 1702.04520, 2026-10-11" }, "hunt2019": { "key": "hunt2019", "authors": "S. Hunt, C. Iliadis, A. E. Champagne, L. N. Downen, A. Cooper", "title": "New measurement of the E(α,lab) = 0.83 MeV resonance in ²²Ne(α,γ)²⁶Mg", "journal": "Phys. Rev. C 99, 045804 (2019)", "year": 2019, "doi": "10.1103/PhysRevC.99.045804", "checked": "APS accepted-manuscript page for the DOI and IAEA EXFOR C2399, 2026-10-11" }, "ota2020": { "key": "ota2020", "authors": "S. Ota, G. Christian et al.", "title": "Decay properties of ²²Ne + α resonances and their impact on s-process nucleosynthesis", "journal": "Phys. Lett. B 802, 135256 (2020)", "year": 2020, "doi": "10.1016/j.physletb.2020.135256", "arxiv": "2001.08206", "checked": "arXiv 2001.08206, DOAJ listing and IAEA EXFOR C2573 (journal reference); DOI from a search listing of the Texas A&M Cyclotron Institute and DOAJ records, consistent with the Elsevier scheme for the article number, 2026-10-11" }, "jayatissa2020": { "key": "jayatissa2020", "authors": "H. Jayatissa, G. V. Rogachev et al.", "title": "Constraining the ²²Ne(α,γ)²⁶Mg and ²²Ne(α,n)²⁵Mg reaction rates using sub-Coulomb α-transfer reactions", "journal": "Phys. Lett. B 802, 135267 (2020)", "year": 2020, "doi": "10.1016/j.physletb.2020.135267", "arxiv": "2001.08316", "checked": "arXiv 2001.08316 (K150 cyclotron, Texas A&M) and IAEA EXFOR C2517 (journal reference); DOI from a search listing, consistent with the Elsevier scheme for the article number, 2026-10-11" }, "piatti2022": { "key": "piatti2022", "authors": "D. Piatti et al. (LUNA Collaboration)", "title": "First direct limit on the 334 keV resonance strength in ²²Ne(α,γ)²⁶Mg reaction", "journal": "Eur. Phys. J. A 58, 194 (2022)", "year": 2022, "doi": "10.1140/epja/s10050-022-00827-2", "arxiv": "2209.03051", "luna": true, "checked": "arXiv 2209.03051, HZDR repository record and published PDF at the University of Bari repository, 2026-10-11" }, "shahina2022": { "key": "shahina2022", "authors": "Shahina, J. Görres, D. Robertson, M. Wiescher et al.", "title": "Direct measurement of the low-energy resonances in ²²Ne(α,γ)²⁶Mg reaction", "journal": "Phys. Rev. C 106, 025805 (2022)", "year": 2022, "doi": "10.1103/PhysRevC.106.025805", "arxiv": "2208.07885", "checked": "arXiv 2208.07885, Sanford Lab publication page (abstract) and JINA Virtual Journal link to the DOI, 2026-10-11" }, "rapagnani2022": { "key": "rapagnani2022", "authors": "D. Rapagnani, C. Ananna, A. Di Leva, G. Imbriani, M. Junker, M. Pignatari, A. Best", "title": "SHADES – ²²Ne(α,n)²⁵Mg reaction rate in the Gamow window", "journal": "EPJ Web Conf. 260, 11031 (2022)", "year": 2022, "doi": "10.1051/epjconf/202226011031", "arxiv": "2510.06268", "checked": "rechecked 2026-10-12 by web search. The EPJ Web of Conferences record for NIC-XVI (volume 260, article 11031, published online 24 February 2022) gives this title, D. Rapagnani as first author and DOI 10.1051/epjconf/202226011031; the arXiv listing 2510.06268, posted 6 October 2025 under physics.ins-det, carries the same title and first author and gives the same journal reference, consistent with a late arXiv posting of the 2022 proceedings" }, "rana2024": { "key": "rana2024", "authors": "T. K. Rana et al.", "title": "New measurement of the Hoyle state radiative transition width", "journal": "Phys. Lett. B 859, 139083 (2024)", "year": 2024, "arxiv": "2311.08781", "checked": "arXiv 2311.08781 (abstract, Γrad/Γ = 4.01(30) × 10⁻⁴ and 4.04(30) × 10⁻⁴ from two experiments, Γrad = 3.75(40) × 10⁻³ eV) and DOAJ listing (Phys. Lett. B, December 2024), by web search, 2026-10-11; volume and article number from a web-search summary of the article and a citing reference list, 2026-10-13; the DOI (probably 10.1016/j.physletb.2024.139083) was searched and not found, so it is omitted" }, "eddington1920": { "key": "eddington1920", "authors": "A. S. Eddington", "title": "The internal constitution of the stars", "journal": "Nature 106, 14 (1920)", "year": 1920, "checked": "volume and page from a Nature-printed copy of the address (Cardiff, 24 August 1920; issue of 2 September 1920) found by search; DOI not confirmed, 2026-10-11" }, "gamow1928": { "key": "gamow1928", "authors": "G. Gamow", "title": "Zur Quantentheorie des Atomkernes", "journal": "Z. Phys. 51, 204 (1928)", "year": 1928, "checked": "first page (received 2 August 1928, Z. Phys. 51, 204) reproduced in a Saarland University course file and cited in arXiv 1508.03578; DOI not confirmed against Springer, 2026-10-11" }, "atkinson1929": { "key": "atkinson1929", "authors": "R. d'E. Atkinson, F. G. Houtermans", "title": "Zur Frage der Aufbaumöglichkeit der Elemente in Sternen", "journal": "Z. Phys. 54, 656 (1929)", "year": 1929, "checked": "volume and page from a Springer reference list (Hahn 1934) and the history in arXiv 2209.00072; one other reference list gives a different page, so check before quoting the page; DOI not confirmed, 2026-10-11" }, "weizsacker1937": { "key": "weizsacker1937", "authors": "C. F. von Weizsäcker", "title": "Über Elementumwandlungen im Innern der Sterne. I", "journal": "Phys. Z. 38, 176 (1937)", "year": 1937, "checked": "citation from a 2006 Physik in unserer Zeit interview and the Nobel bibliography search, 2026-10-11" }, "weizsacker1938": { "key": "weizsacker1938", "authors": "C. F. von Weizsäcker", "title": "Über Elementumwandlungen im Innern der Sterne. II", "journal": "Phys. Z. 39, 633 (1938)", "year": 1938, "checked": "Nobel Prize bibliography and Physikalische Zeitschrift reference list (pp. 633–646), 2026-10-11" }, "bethe1938": { "key": "bethe1938", "authors": "H. A. Bethe, C. L. Critchfield", "title": "The formation of deuterons by proton combination", "journal": "Phys. Rev. 54, 248 (1938)", "year": 1938, "doi": "10.1103/PhysRev.54.248", "checked": "Crossref record and APS issue table (published 15 August 1938), 2026-10-11" }, "bethe1939": { "key": "bethe1939", "authors": "H. A. Bethe", "title": "Energy production in stars", "journal": "Phys. Rev. 55, 434 (1939)", "year": 1939, "doi": "10.1103/PhysRev.55.434", "checked": "INSPIRE record and APS issue listing (published 1 March 1939), 2026-10-11" }, "alpher1948": { "key": "alpher1948", "authors": "R. A. Alpher, H. Bethe, G. Gamow", "title": "The origin of chemical elements", "journal": "Phys. Rev. 73, 803 (1948)", "year": 1948, "doi": "10.1103/PhysRev.73.803", "checked": "bibcode 1948PhRv...73..803A and DOI from reference records found by search (published 1 April 1948), 2026-10-11" }, "salpeter1952": { "key": "salpeter1952", "authors": "E. E. Salpeter", "title": "Nuclear reactions in stars without hydrogen", "journal": "Astrophys. J. 115, 326 (1952)", "year": 1952, "checked": "journal reference from a Cambridge-hosted bibliography and Salpeter's own retrospective (arXiv 0711.3139); DOI not confirmed, 2026-10-11" }, "dunbar1953": { "key": "dunbar1953", "authors": "D. N. F. Dunbar, R. E. Pixley, W. A. Wenzel, W. Whaling", "title": "The 7.68-MeV state in C¹²", "journal": "Phys. Rev. 92, 649 (1953)", "year": 1953, "doi": "10.1103/PhysRev.92.649", "checked": "Caltech Authors record (published 1 November 1953), 2026-10-11" }, "hoyle1954": { "key": "hoyle1954", "authors": "F. Hoyle", "title": "On nuclear reactions occurring in very hot stars. I. The synthesis of elements from carbon to nickel", "journal": "Astrophys. J. Suppl. 1, 121 (1954)", "year": 1954, "url": "https://ui.adsabs.harvard.edu/abs/1954ApJS....1..121H/abstract", "checked": "ADS record 1954ApJS....1..121H; DOI not confirmed, 2026-10-11" }, "cook1957": { "key": "cook1957", "authors": "C. W. Cook, W. A. Fowler, C. C. Lauritsen, T. Lauritsen", "title": "B¹², C¹², and the red giants", "journal": "Phys. Rev. 107, 508 (1957)", "year": 1957, "doi": "10.1103/PhysRev.107.508", "checked": "reference list giving volume, page and DOI, and the related Caltech PhD thesis of C. W. Cook (1957), 2026-10-11" }, "b2fh1957": { "key": "b2fh1957", "authors": "E. M. Burbidge, G. R. Burbidge, W. A. Fowler, F. Hoyle", "title": "Synthesis of the elements in stars", "journal": "Rev. Mod. Phys. 29, 547 (1957)", "year": 1957, "doi": "10.1103/RevModPhys.29.547", "checked": "INSPIRE record (pp. 547–650), 2026-10-11" }, "cameron1957": { "key": "cameron1957", "authors": "A. G. W. Cameron", "title": "Nuclear reactions in stars and nucleogenesis", "journal": "Publ. Astron. Soc. Pac. 69, 201 (1957)", "year": 1957, "url": "https://articles.adsabs.harvard.edu/pdf/1957PASP...69..201C", "checked": "ADS scan 1957PASP...69..201C (June 1957); DOI not confirmed, 2026-10-11" }, "fowler1984": { "key": "fowler1984", "authors": "W. A. Fowler", "title": "Experimental and theoretical nuclear astrophysics: the quest for the origin of the elements", "journal": "Rev. Mod. Phys. 56, 149 (1984)", "year": 1984, "doi": "10.1103/RevModPhys.56.149", "checked": "CiNii record (pp. 149–179, 1 April 1984); Nobel lecture, 2026-10-11" }, "davis1968": { "key": "davis1968", "authors": "R. Davis Jr., D. S. Harmer, K. C. Hoffman", "title": "Search for neutrinos from the Sun", "journal": "Phys. Rev. Lett. 20, 1205 (1968)", "year": 1968, "doi": "10.1103/PhysRevLett.20.1205", "checked": "INSPIRE record and APS issue page (published 20 May 1968), 2026-10-11" }, "bahcall1968": { "key": "bahcall1968", "authors": "J. N. Bahcall, N. A. Bahcall, G. Shaviv", "title": "Present status of the theoretical predictions for the ³⁷Cl solar-neutrino experiment", "journal": "Phys. Rev. Lett. 20, 1209 (1968)", "year": 1968, "checked": "Princeton and Caltech repository records (pp. 1209–1212); DOI not confirmed, 2026-10-11" }, "hirata1987": { "key": "hirata1987", "authors": "K. Hirata et al. (Kamiokande-II Collaboration)", "title": "Observation of a neutrino burst from the supernova SN1987A", "journal": "Phys. Rev. Lett. 58, 1490 (1987)", "year": 1987, "doi": "10.1103/PhysRevLett.58.1490", "checked": "APS issue listing (published 6 April 1987) and DOI in several reference lists, 2026-10-11" }, "hirata1989": { "key": "hirata1989", "authors": "K. S. Hirata et al. (Kamiokande-II Collaboration)", "title": "Observation of ⁸B solar neutrinos in the Kamiokande-II detector", "journal": "Phys. Rev. Lett. 63, 16 (1989)", "year": 1989, "checked": "KEK Kamiokande publication list and later reference lists; DOI not confirmed, 2026-10-11" }, "abazov1991": { "key": "abazov1991", "authors": "A. I. Abazov et al. (SAGE)", "title": "Search for neutrinos from the Sun using the reaction ⁷¹Ga(νₑ,e⁻)⁷¹Ge", "journal": "Phys. Rev. Lett. 67, 3332 (1991)", "year": 1991, "checked": "INIS record (pp. 3332–3335, issue of 9 December 1991); DOI not confirmed, 2026-10-11" }, "gallex1992": { "key": "gallex1992", "authors": "GALLEX Collaboration", "title": "Solar neutrinos observed by GALLEX at Gran Sasso", "journal": "Phys. Lett. B 285, 376 (1992)", "year": 1992, "doi": "10.1016/0370-2693(92)91521-A", "checked": "Heidelberg and Tor Vergata library records, 2026-10-11" }, "fukuda1998": { "key": "fukuda1998", "authors": "Y. Fukuda et al. (Super-Kamiokande Collaboration)", "title": "Evidence for oscillation of atmospheric neutrinos", "journal": "Phys. Rev. Lett. 81, 1562 (1998)", "year": 1998, "doi": "10.1103/PhysRevLett.81.1562", "arxiv": "hep-ex/9807003", "checked": "arXiv hep-ex/9807003 listing with journal DOI, 2026-10-11" }, "sno2002": { "key": "sno2002", "authors": "Q. R. Ahmad et al. (SNO Collaboration)", "title": "Direct evidence for neutrino flavor transformation from neutral-current interactions in the Sudbury Neutrino Observatory", "journal": "Phys. Rev. Lett. 89, 011301 (2002)", "year": 2002, "doi": "10.1103/PhysRevLett.89.011301", "arxiv": "nucl-ex/0204008", "checked": "arXiv nucl-ex/0204008 and INSPIRE record, 2026-10-11" }, "davis2003": { "key": "davis2003", "authors": "R. Davis Jr.", "title": "Nobel lecture: A half-century with solar neutrinos", "journal": "Rev. Mod. Phys. 75, 985 (2003)", "year": 2003, "checked": "journal header of the published lecture (published 8 August 2003) and nobelprize.org lecture page; DOI not confirmed, 2026-10-11" }, "borexino2008": { "key": "borexino2008", "authors": "Borexino Collaboration", "title": "First real time detection of ⁷Be solar neutrinos by Borexino", "journal": "Phys. Lett. B 658, 101 (2008)", "year": 2008, "arxiv": "0708.2251", "checked": "arXiv 0708.2251 (submitted 16 August 2007) and journal record (pp. 101–108); DOI not confirmed, 2026-10-11" }, "borexino2014": { "key": "borexino2014", "authors": "G. Bellini et al. (Borexino Collaboration)", "title": "Neutrinos from the primary proton–proton fusion process in the Sun", "journal": "Nature 512, 383 (2014)", "year": 2014, "doi": "10.1038/nature13702", "checked": "Mainz, Princeton and TUM records (published 28 August 2014), 2026-10-11" }, "mahoney1984": { "key": "mahoney1984", "authors": "W. A. Mahoney, J. C. Ling, W. A. Wheaton, A. S. Jacobson", "title": "HEAO 3 discovery of Al-26 in the interstellar medium", "journal": "Astrophys. J. 286, 578 (1984)", "year": 1984, "checked": "authors, title and year from NASA NTRS and the citation in arXiv astro-ph/0304508; volume and page not independently confirmed, 2026-10-11" }, "abbott2017": { "key": "abbott2017", "authors": "B. P. Abbott et al. (LIGO Scientific and Virgo Collaborations)", "title": "GW170817: Observation of gravitational waves from a binary neutron star inspiral", "journal": "Phys. Rev. Lett. 119, 161101 (2017)", "year": 2017, "doi": "10.1103/PhysRevLett.119.161101", "arxiv": "1710.05832", "checked": "Strathclyde and Caltech repository records and arXiv listing, 2026-10-11" }, "pian2017": { "key": "pian2017", "authors": "E. Pian et al.", "title": "Spectroscopic identification of r-process nucleosynthesis in a double neutron-star merger", "journal": "Nature 551, 67 (2017)", "year": 2017, "doi": "10.1038/nature24298", "arxiv": "1710.05858", "checked": "ADS record 2017Natur.551...67P and Warwick repository, 2026-10-11" }, "greife1994": { "key": "greife1994", "authors": "U. Greife et al.", "title": "Laboratory for Underground Nuclear Astrophysics (LUNA)", "journal": "Nucl. Instrum. Methods A 350, 327 (1994)", "year": 1994, "luna": true, "checked": "INSPIRE and Caltech Authors records (pp. 327–337, October 1994); DOI not confirmed against the publisher, 2026-10-11" }, "bonetti1999": { "key": "bonetti1999", "authors": "R. Bonetti et al. (LUNA Collaboration)", "title": "First measurement of the ³He(³He,2p)⁴He cross section down to the lower edge of the solar Gamow peak", "journal": "Phys. Rev. Lett. 82, 5205 (1999)", "year": 1999, "doi": "10.1103/PhysRevLett.82.5205", "arxiv": "nucl-ex/9902004", "luna": true, "checked": "arXiv nucl-ex/9902004 and Naples IRIS record, 2026-10-11" }, "formicola2003": { "key": "formicola2003", "authors": "A. Formicola et al.", "title": "The LUNA II 400 kV accelerator", "journal": "Nucl. Instrum. Methods A 507, 609 (2003)", "year": 2003, "doi": "10.1016/S0168-9002(03)01435-9", "luna": true, "checked": "INFN open-access repository record (pp. 609–616), 2026-10-11" }, "broggini2010": { "key": "broggini2010", "authors": "C. Broggini, D. Bemmerer, A. Guglielmetti, R. Menegazzo", "title": "LUNA: Nuclear astrophysics deep underground", "journal": "Annu. Rev. Nucl. Part. Sci. 60, 53 (2010)", "year": 2010, "doi": "10.1146/annurev.nucl.012809.104526", "arxiv": "1010.4165", "luna": true, "checked": "arXiv 1010.4165 listing with journal reference and DOI, 2026-10-11" }, "sen2019": { "key": "sen2019", "authors": "A. Sen, G. Domínguez-Cañizares, N. C. Podaru, D. J. W. Mous, M. Junker, G. Imbriani, V. Rigato", "title": "A high intensity, high stability 3.5 MV Singletron accelerator", "journal": "Nucl. Instrum. Methods B 450, 390 (2019)", "year": 2019, "doi": "10.1016/j.nimb.2018.09.016", "luna": true, "checked": "Naples IRIS record (pp. 390–395), 2026-10-11" }, "mossa2020": { "key": "mossa2020", "authors": "V. Mossa et al. (LUNA Collaboration)", "title": "The baryon density of the Universe from an improved rate of deuterium burning", "journal": "Nature 587, 210 (2020)", "year": 2020, "doi": "10.1038/s41586-020-2878-4", "luna": true, "checked": "RePEc and INAF repository records, 2026-10-11" }, "junker2023": { "key": "junker2023", "authors": "M. Junker, G. Imbriani, A. Best, A. Boeltzig, A. Compagnucci, A. Di Leva, F. Ferraro, D. Rapagnani, V. Rigato", "title": "The deep underground Bellotti Ion Beam Facility – status and perspectives", "journal": "Front. Phys. 11, 1291113 (2023)", "year": 2023, "doi": "10.3389/fphy.2023.1291113", "checked": "DOAJ and HZDR publication records (published 9 November 2023), 2026-10-11" }, "broggini2018": { "key": "broggini2018", "authors": "C. Broggini, D. Bemmerer, A. Caciolli, D. Trezzi", "title": "LUNA: Status and prospects", "journal": "Prog. Part. Nucl. Phys. 98, 55 (2018)", "year": 2018, "arxiv": "1707.07952", "luna": true, "checked": "arXiv 1707.07952 listing (authors, title; v4 of 30 November 2017, later marked withdrawn by the first author) and the journal reference (pp. 55–84) as cited in a 2026 LUNA paper; DOI not confirmed, 2026-10-11" }, "broggini2019": { "key": "broggini2019", "authors": "C. Broggini, O. Straniero, M. G. F. Taiuti et al.", "title": "Experimental nuclear astrophysics in Italy", "journal": "Riv. Nuovo Cimento 42, 103 (2019)", "year": 2019, "doi": "10.1393/ncr/i2019-10157-1", "arxiv": "1902.05262", "checked": "Italian university repository records (vol. 42, no. 3, pp. 103–152, with DOI) and arXiv 1902.05262, 2026-10-11" }, "rogalla1999": { "key": "rogalla1999", "authors": "D. Rogalla et al.", "title": "Recoil separator ERNA: ion beam specifications", "journal": "Eur. Phys. J. A 6, 471 (1999)", "year": 1999, "checked": "EPJ A abstract page (1999) and later ERNA papers (pp. 471–477); DOI not confirmed, 2026-10-11" }, "hutcheon2003": { "key": "hutcheon2003", "authors": "D. A. Hutcheon et al.", "title": "The DRAGON facility for nuclear astrophysics at TRIUMF-ISAC: design, construction and operation", "journal": "Nucl. Instrum. Methods A 498, 190 (2003)", "year": 2003, "checked": "title, first author and journal from the TRIUMF astrophysics publication list and the McMaster record; volume and page not independently confirmed; DOI not confirmed, 2026-10-11" }, "couder2008": { "key": "couder2008", "authors": "M. Couder, G. P. A. Berg, J. Görres, P. J. LeBlanc, L. O. Lamm, E. Stech, M. Wiescher, J. Hinnefeldt", "title": "Design of the recoil mass separator St. George", "journal": "Nucl. Instrum. Methods A 587, 35 (2008)", "year": 2008, "checked": "publication record found by search (pp. 35–45, online December 2007); DOI not confirmed, 2026-10-11" }, "guerrero2013": { "key": "guerrero2013", "authors": "C. Guerrero et al. (n_TOF Collaboration)", "title": "Performance of the neutron time-of-flight facility n_TOF at CERN", "journal": "Eur. Phys. J. A 49, 27 (2013)", "year": 2013, "doi": "10.1140/epja/i2013-13027-6", "checked": "University of Hertfordshire, Manchester and JRC repository records, 2026-10-11" }, "zhang2022": { "key": "zhang2022", "authors": "L. Zhang et al. (JUNA Collaboration)", "title": "Measurement of ¹⁹F(p,γ)²⁰Ne reaction suggests CNO breakout in first stars", "journal": "Nature 610, 656 (2022)", "year": 2022, "doi": "10.1038/s41586-022-05230-x", "arxiv": "2302.09802", "checked": "RePEc record and Springer article page (published 27 October 2022) and arXiv 2302.09802; end page not confirmed, 2026-10-11" }, "baur1986": { "key": "baur1986", "authors": "G. Baur, C. A. Bertulani, H. Rebel", "title": "Coulomb dissociation as a source of information on radiative capture processes of astrophysical interest", "journal": "Nucl. Phys. A 458, 188 (1986)", "year": 1986, "checked": "reference lists giving pp. 188–204 and the Karlsruhe preprint KfK 4032 (January 1986) with the same title; DOI not confirmed, 2026-10-11" }, "tribble2014": { "key": "tribble2014", "authors": "R. E. Tribble, C. A. Bertulani, M. La Cognata, A. M. Mukhamedzhanov, C. Spitaleri", "title": "Indirect techniques in nuclear astrophysics: a review", "journal": "Rep. Prog. Phys. 77, 106901 (2014)", "year": 2014, "doi": "10.1088/0034-4885/77/10/106901", "checked": "Texas A&M Cyclotron Institute publication record, 2026-10-11" }, "tumino2021": { "key": "tumino2021", "authors": "A. Tumino, C. A. Bertulani, M. La Cognata et al.", "title": "The Trojan Horse method: a nuclear physics tool for astrophysics", "journal": "Annu. Rev. Nucl. Part. Sci. 71, 345 (2021)", "year": 2021, "checked": "title, authors Tumino, Bertulani and La Cognata, volume and first page from an indexed record and a seminar citation (second check by search); DOI not confirmed, 2026-10-11" }, "casey2017": { "key": "casey2017", "authors": "D. T. Casey et al.", "title": "Thermonuclear reactions probed at stellar-core conditions with laser-based inertial-confinement fusion", "journal": "Nat. Phys. 13, 1227 (2017)", "year": 2017, "doi": "10.1038/nphys4220", "checked": "Princeton research portal and OSTI record 1404861; LLNL news release, 2026-10-11" }, "bahcall1964": { "key": "bahcall1964", "authors": "J. N. Bahcall", "title": "Solar neutrinos. I. Theoretical", "journal": "Phys. Rev. Lett. 12, 300 (1964)", "year": 1964, "checked": "volume and page from Bahcall's popular account (arXiv physics/0411190) and other reference lists; title from the standard citation, not seen on the APS page; DOI not confirmed, 2026-10-11" }, "adelberger1998": { "key": "adelberger1998", "authors": "E. G. Adelberger et al.", "title": "Solar fusion cross sections", "journal": "Rev. Mod. Phys. 70, 1265 (1998)", "year": 1998, "doi": "10.1103/RevModPhys.70.1265", "arxiv": "astro-ph/9805121", "checked": "arXiv astro-ph/9805121 listing and NCSU repository record (pp. 1265–1291), 2026-10-11" }, "iliadis2010": { "key": "iliadis2010", "authors": "C. Iliadis, R. Longland, A. E. Champagne, A. Coc, R. Fitzgerald", "title": "Charged-particle thermonuclear reaction rates: II. Tables and graphs of reaction rates and probability density functions", "journal": "Nucl. Phys. A 841, 31 (2010)", "year": 2010, "doi": "10.1016/j.nuclphysa.2010.04.009", "arxiv": "1004.4517", "checked": "arXiv 1004.4517 and NIST publication record (authors, DOI) found by search; volume 841 from the companion record of paper I, start page 31 not displayed by a record, 2026-10-11" }, "lyons2018": { "key": "lyons2018", "authors": "S. Lyons et al.", "title": "Determination of ²⁰Ne(p,γ)²¹Na cross sections from Eₚ = 500–2000 keV", "journal": "Phys. Rev. C 97, 065802 (2018)", "year": 2018, "doi": "10.1103/PhysRevC.97.065802", "checked": "JINA Virtual Journal listing and APS accepted-manuscript link (link.aps.org/accepted/10.1103/PhysRevC.97.065802) found by search, 2026-10-11" }, "masha2023": { "key": "masha2023", "authors": "E. Masha, L. Barbieri, J. Skowronski et al. (LUNA Collaboration)", "title": "First measurement of the low-energy direct capture in ²⁰Ne(p,γ)²¹Na and improved energy and strength of the E_cm = 368 keV resonance", "journal": "Phys. Rev. C 108, L052801 (2023)", "year": 2023, "doi": "10.1103/PhysRevC.108.L052801", "arxiv": "2311.04089", "luna": true, "checked": "arXiv 2311.04089 and Genoa IRIS copy of the published letter found by search; DOI from the author's publication list (content/publications.yaml), 2026-10-11" }, "caciolli2025": { "key": "caciolli2025", "authors": "A. Caciolli (LUNA Collaboration)", "title": "Study of the ²⁰Ne(p,γ)²¹Na reaction at LUNA", "year": 2025, "arxiv": "2510.01884", "luna": true, "checked": "arXiv 2510.01884 listing found by search (conference contribution submitted 2 October 2025 by A. Caciolli for the LUNA Collaboration; preliminary results); no journal reference shown, 2026-10-11" }, "sidhu2025": { "key": "sidhu2025", "authors": "R. S. Sidhu et al. (LUNA Collaboration)", "title": "Improved direct measurement of low-energy resonances in the ²¹Ne(p,γ)²²Na reaction", "journal": "Phys. Rev. C 112, L052801 (2025)", "year": 2025, "doi": "10.1103/vqt1-jxpw", "arxiv": "2505.22426", "luna": true, "checked": "arXiv 2505.22426 and Milan AIR copy of the published letter found by search (volume, article number, dates); DOI from the author's publication list (content/publications.yaml), 2026-10-11" }, "cavanna2014": { "key": "cavanna2014", "authors": "F. Cavanna et al. (LUNA Collaboration)", "title": "A new study of the ²²Ne(p,γ)²³Na reaction deep underground: feasibility, setup, and first observation of the 186 keV resonance", "journal": "Eur. Phys. J. A 50, 179 (2014)", "year": 2014, "doi": "10.1140/epja/i2014-14179-5", "arxiv": "1411.2888", "luna": true, "checked": "EPJ A abstract page, arXiv 1411.2888 and Turin IRIS record found by search, 2026-10-11" }, "depalo2015": { "key": "depalo2015", "authors": "R. Depalo et al.", "title": "Strengths of the resonances at 436, 479, 639, 661, and 1279 keV in the ²²Ne(p,γ)²³Na reaction", "journal": "Phys. Rev. C 92, 045807 (2015)", "year": 2015, "doi": "10.1103/PhysRevC.92.045807", "arxiv": "1507.03893", "checked": "HZDR publication record (journal reference and arXiv id) and Padua repository record found by search; DOI by APS scheme from the confirmed journal reference, 2026-10-11" }, "cavanna2015": { "key": "cavanna2015", "authors": "F. Cavanna et al. (LUNA Collaboration)", "title": "Three new low-energy resonances in the ²²Ne(p,γ)²³Na reaction", "journal": "Phys. Rev. Lett. 115, 252501 (2015)", "year": 2015, "doi": "10.1103/PhysRevLett.115.252501", "arxiv": "1511.05329", "luna": true, "checked": "arXiv 1511.05329, INAF and HZDR repository records found by search; DOI by APS scheme from the confirmed journal reference, 2026-10-11" }, "cavanna2018": { "key": "cavanna2018", "authors": "F. Cavanna et al. (LUNA Collaboration)", "title": "Erratum: Three new low-energy resonances in the ²²Ne(p,γ)²³Na reaction", "journal": "Phys. Rev. Lett. 120, 239901 (2018)", "year": 2018, "doi": "10.1103/PhysRevLett.120.239901", "luna": true, "checked": "Milan AIR and Edinburgh research portal records found by search, 2026-10-11" }, "depalo2016": { "key": "depalo2016", "authors": "R. Depalo et al. (LUNA Collaboration)", "title": "Direct measurement of low-energy ²²Ne(p,γ)²³Na resonances", "journal": "Phys. Rev. C 94, 055804 (2016)", "year": 2016, "doi": "10.1103/PhysRevC.94.055804", "arxiv": "1610.00925", "luna": true, "checked": "arXiv 1610.00925, JINA Virtual Journal and HZDR records found by search, 2026-10-11" }, "kelly2017": { "key": "kelly2017", "authors": "K. J. Kelly, A. E. Champagne, L. N. Downen, J. R. Dermigny, S. Hunt, C. Iliadis, A. L. Cooper", "title": "New measurements of low-energy resonances in the ²²Ne(p,γ)²³Na reaction", "journal": "Phys. Rev. C 95, 015806 (2017)", "year": 2017, "doi": "10.1103/PhysRevC.95.015806", "checked": "EXFOR entry C2254 (title, authors, journal reference, LENA setup) and the reference list of arXiv 1910.01698, found by search; DOI by APS scheme from the confirmed journal reference, 2026-10-11" }, "ferraro2018": { "key": "ferraro2018", "authors": "F. Ferraro et al. (LUNA Collaboration)", "title": "Direct capture cross section and the Eₚ = 71 and 105 keV resonances in the ²²Ne(p,γ)²³Na reaction", "journal": "Phys. Rev. Lett. 121, 172701 (2018)", "year": 2018, "doi": "10.1103/PhysRevLett.121.172701", "arxiv": "1810.01628", "luna": true, "checked": "arXiv 1810.01628, HZDR record, JINA Virtual Journal and UK REF database (DOI) found by search, 2026-10-11" }, "lennarz2020": { "key": "lennarz2020", "authors": "A. Lennarz et al.", "title": "First inverse kinematics measurement of key resonances in the ²²Ne(p,γ)²³Na reaction at stellar temperatures", "journal": "Phys. Lett. B 807, 135539 (2020)", "year": 2020, "doi": "10.1016/j.physletb.2020.135539", "arxiv": "1910.00791", "checked": "arXiv 1910.00791, White Rose eprint and DOAJ records found by search, 2026-10-11; 458 keV strength rechecked by web search (ωγ = 0.439(22) eV from singles, 0.441(50) eV from coincidences; not in agreement with the two latest results, in agreement with three earlier values), 2026-10-13" }, "williams2020": { "key": "williams2020", "authors": "M. Williams et al.", "title": "First inverse kinematics study of the ²²Ne(p,γ)²³Na reaction and its role in AGB star and classical nova nucleosynthesis", "journal": "Phys. Rev. C 102, 035801 (2020)", "year": 2020, "doi": "10.1103/PhysRevC.102.035801", "arxiv": "1910.01698", "checked": "arXiv 1910.01698, White Rose record and EXFOR entry C2582 found by search, 2026-10-11" }, "takacs2024": { "key": "takacs2024", "authors": "M. P. Takács et al. (LUNA Collaboration)", "title": "Direct capture cross section and resonances in the ²²Ne(p,γ)²³Na reaction at low energy", "journal": "Phys. Rev. C 109, 064627 (2024)", "year": 2024, "doi": "10.1103/PhysRevC.109.064627", "luna": true, "checked": "author's publication list (content/publications.yaml); journal reference also cited in a 2024 LUNA conference talk found by search; title, PRC June 2024 and abstract (branchings of the 156.2 and 259.7 keV resonances, direct capture down to Ep = 188 keV) confirmed by the University of Edinburgh research portal record, 2026-10-11" }, "cesaratto2013": { "key": "cesaratto2013", "authors": "J. M. Cesaratto et al.", "title": "Measurement of the E_c.m. = 138 keV resonance in the ²³Na(p,γ)²⁴Mg reaction and the abundance of sodium in AGB stars", "journal": "Phys. Rev. C 88, 065806 (2013)", "year": 2013, "doi": "10.1103/PhysRevC.88.065806", "checked": "EXFOR entry C2076 (title, journal reference, LENA setup) found by search; DOI by APS scheme from the confirmed journal reference, 2026-10-11" }, "boeltzig2019": { "key": "boeltzig2019", "authors": "A. Boeltzig et al. (LUNA Collaboration)", "title": "Direct measurements of low-energy resonance strengths of the ²³Na(p,γ)²⁴Mg reaction for astrophysics", "journal": "Phys. Lett. B 795, 122 (2019)", "year": 2019, "doi": "10.1016/j.physletb.2019.05.044", "luna": true, "checked": "Edinburgh research portal, Turin IRIS, DOAJ and NSF PAR records found by search (pages 122–128, DOI); arXiv id not seen, 2026-10-11" }, "boeltzig2022": { "key": "boeltzig2022", "authors": "A. Boeltzig, R. J. deBoer et al.", "title": "Investigation of direct capture in the ²³Na(p,γ)²⁴Mg reaction", "journal": "Phys. Rev. C 106, 045801 (2022)", "year": 2022, "doi": "10.1103/PhysRevC.106.045801", "checked": "APS accepted-manuscript link, JINA Virtual Journal and NSF PAR records found by search, 2026-10-11" }, "marshall2023": { "key": "marshall2023", "authors": "C. Marshall, K. Setoodehnia, G. C. Cinquegrana, J. H. Kelly, F. Portillo Chaves, A. Karakas, R. Longland", "title": "New constraints on sodium production in globular clusters from the ²³Na(³He,d)²⁴Mg reaction", "journal": "Phys. Rev. C 107, 035806 (2023)", "year": 2023, "doi": "10.1103/PhysRevC.107.035806", "arxiv": "2303.06128", "checked": "arXiv 2303.06128, APS accepted-manuscript link and JINA Virtual Journal listing found by search, 2026-10-11" }, "hale2004": { "key": "hale2004", "authors": "S. E. Hale et al.", "title": "Investigation of the ²³Na(p,γ)²⁴Mg and ²³Na(p,α)²⁰Ne reactions via (³He,d) spectroscopy", "journal": "Phys. Rev. C 70, 045802 (2004)", "year": 2004, "doi": "10.1103/PhysRevC.70.045802", "checked": "LSU Digital Commons record and JINA Virtual Journal listing (title, journal reference, abstract) found by search; DOI by APS scheme, 2026-10-11" }, "limata2010": { "key": "limata2010", "authors": "B. Limata et al. (LUNA Collaboration)", "title": "New experimental study of low-energy (p,γ) resonances in magnesium isotopes", "journal": "Phys. Rev. C 82, 015801 (2010)", "year": 2010, "doi": "10.1103/PhysRevC.82.015801", "arxiv": "1006.5281", "luna": true, "checked": "arXiv 1006.5281, HZDR and INIS records found by search, 2026-10-11" }, "strieder2012": { "key": "strieder2012", "authors": "F. Strieder et al. (LUNA Collaboration)", "title": "The ²⁵Mg(p,γ)²⁶Al reaction at low astrophysical energies", "journal": "Phys. Lett. B 707, 60 (2012)", "year": 2012, "doi": "10.1016/j.physletb.2011.12.029", "arxiv": "1112.3313", "luna": true, "checked": "arXiv 1112.3313 and HZDR publication record found by search, 2026-10-11" }, "straniero2013": { "key": "straniero2013", "authors": "O. Straniero et al. (LUNA Collaboration)", "title": "Impact of a revised ²⁵Mg(p,γ)²⁶Al reaction rate on the operation of the Mg-Al cycle", "journal": "Astrophys. J. 763, 100 (2013)", "year": 2013, "arxiv": "1211.6661", "luna": true, "checked": "arXiv 1211.6661, Atomki, MTAK and Turin repository records (ADS bibcode 2013ApJ...763..100S) found by search; DOI not seen, omitted, 2026-10-11" }, "su2022": { "key": "su2022", "authors": "J. Su, H. Zhang, Z. H. Li et al. (JUNA Collaboration)", "title": "First result from the Jinping Underground Nuclear Astrophysics experiment JUNA: precise measurement of the 92 keV ²⁵Mg(p,γ)²⁶Al resonance", "journal": "Sci. Bull. 67, 125 (2022)", "year": 2022, "checked": "title from a SciSpace author listing; journal reference from the reference list of a later JUNA review (Chinese Physics Letters) found by search; DOI not seen, omitted, 2026-10-11" }, "iliadis1990": { "key": "iliadis1990", "authors": "C. Iliadis et al.", "title": "Low-energy resonances in ²⁵Mg(p,γ)²⁶Al, ²⁶Mg(p,γ)²⁷Al and ²⁷Al(p,γ)²⁸Si", "journal": "Nucl. Phys. A 512, 509 (1990)", "year": 1990, "checked": "Atomki APHA publication listings (title, journal reference) and the ENSDF ²⁷Al(p,γ) evaluation reference list found by search; DOI not seen, omitted, 2026-10-11" }, "harissopulos2000": { "key": "harissopulos2000", "authors": "S. Harissopulos et al.", "title": "The ²⁷Al(p,γ)²⁸Si reaction: direct capture cross-section and resonance strengths at Eₚ = 0.2–1.12 MeV", "journal": "Eur. Phys. J. A 9, 479 (2000)", "year": 2000, "checked": "EPJ A abstract page (title, abstract) and IAEA EXFOR entry found by search; DOI not seen, omitted, 2026-10-11" }, "palmerini2021": { "key": "palmerini2021", "authors": "S. Palmerini, M. La Cognata et al.", "title": "The ²⁷Al(p,α)²⁴Mg reaction at astrophysical energies studied by means of the Trojan Horse Method applied to the ²H(²⁷Al,α²⁴Mg)n reaction", "journal": "Eur. Phys. J. Plus 136 (2021)", "year": 2021, "doi": "10.1140/epjp/s13360-021-01872-4", "arxiv": "2108.06145", "checked": "arXiv 2108.06145 and a repository record giving journal, volume and DOI, found by search; article number not seen, 2026-10-11" }, "lacognata2022": { "key": "lacognata2022", "authors": "M. La Cognata et al.", "title": "Exploring the astrophysical energy range of the ²⁷Al(p,α)²⁴Mg reaction: a new recommended reaction rate", "journal": "Phys. Lett. B 826, 136917 (2022)", "year": 2022, "doi": "10.1016/j.physletb.2022.136917", "checked": "DOAJ listing and abstract (journal, article number, DOI) found by search, 2026-10-11" }, "ananna2024": { "key": "ananna2024", "authors": "C. Ananna et al. (LUNA Collaboration)", "title": "Detectors and shieldings: past and future at LUNA", "journal": "Universe 10, 228 (2024)", "year": 2024, "doi": "10.3390/universe10050228", "luna": true, "checked": "author's publication list (content/publications.yaml); a search hit for the same review describes the planned LUNA campaign on the 133 keV ²³Na(p,α)²⁰Ne resonance, 2026-10-11" }, "kankainen2021": { "key": "kankainen2021", "authors": "A. Kankainen et al.", "title": "Decay of the key 92-keV resonance in the ²⁵Mg(p,γ) reaction to the ground and isomeric states of the cosmic γ-ray emitter ²⁶Al", "journal": "Phys. Lett. B 813, 136033 (2021)", "year": 2021, "doi": "10.1016/j.physletb.2020.136033", "checked": "University of Jyväskylä JYX repository record and DOAJ listing (Phys. Lett. B, February 2021; abstract with f₀ = 0.52(2)(6)), IAEA EXFOR entry C2632 (ATLAS, Argonne) and the DOI as given in a second search, 2026-10-11" }, "descouvemont2004": { "key": "descouvemont2004", "authors": "P. Descouvemont, A. Adahchour, C. Angulo, A. Coc, E. Vangioni-Flam", "title": "Compilation and R-matrix analysis of Big Bang nuclear reaction rates", "journal": "At. Data Nucl. Data Tables 88, 203 (2004)", "year": 2004, "arxiv": "astro-ph/0407101", "checked": "arXiv astro-ph/0407101 listing and UCLouvain repository record (vol. 88, pp. 203–236); DOI not seen, 2026-10-11" }, "fields2020": { "key": "fields2020", "authors": "B. D. Fields, K. A. Olive, T.-H. Yeh, C. Young", "title": "Big-Bang Nucleosynthesis after Planck", "journal": "JCAP 03, 010 (2020); erratum JCAP 11, E02 (2020)", "year": 2020, "doi": "10.1088/1475-7516/2020/03/010", "arxiv": "1912.01132", "checked": "arXiv 1912.01132 and University of Minnesota records of the article and erratum; DOI follows the IOP JCAP scheme, 2026-10-11" }, "iliadis2020": { "key": "iliadis2020", "authors": "C. Iliadis, A. Coc", "title": "Thermonuclear reaction rates and primordial nucleosynthesis", "journal": "Astrophys. J. 901, 127 (2020)", "year": 2020, "arxiv": "2008.12200", "checked": "arXiv 2008.12200, HAL record hal-02946231 and TUNL publication list; DOI not seen, 2026-10-11" }, "pisanti2021": { "key": "pisanti2021", "authors": "O. Pisanti, G. Mangano, G. Miele, P. Mazzella", "title": "Primordial deuterium after LUNA: concordances and error budget", "journal": "JCAP 04, 020 (2021)", "year": 2021, "doi": "10.1088/1475-7516/2021/04/020", "arxiv": "2011.11537", "checked": "arXiv 2011.11537 listing, which links the JCAP DOI, 2026-10-11" }, "ma1997": { "key": "ma1997", "authors": "L. Ma, H. J. Karwowski, C. R. Brune et al.", "title": "Measurements of ¹H(d⃗,γ)³He and ²H(p⃗,γ)³He at very low energies", "journal": "Phys. Rev. C 55, 588 (1997)", "year": 1997, "doi": "10.1103/PhysRevC.55.588", "checked": "OSTI records 450481 and 804151 and ACNP index (vol. 55, pp. 588–596); DOI from the APS scheme, 2026-10-11" }, "schmid1997": { "key": "schmid1997", "authors": "G. J. Schmid et al.", "title": "The ²H(p⃗,γ)³He and ¹H(d⃗,γ)³He reactions below 80 keV", "journal": "Phys. Rev. C 56, 2565 (1997)", "year": 1997, "doi": "10.1103/PhysRevC.56.2565", "checked": "INIS record and Duke Scholars record, DOI quoted there, 2026-10-11" }, "casella2002": { "key": "casella2002", "authors": "C. Casella et al. (LUNA Collaboration)", "title": "First measurement of the d(p,γ)³He cross section down to the solar Gamow peak", "journal": "Nucl. Phys. A 706, 203 (2002)", "year": 2002, "doi": "10.1016/S0375-9474(02)00749-2", "luna": true, "checked": "University of Naples and Turin IRIS records (DOI and pages 203–216), 2026-10-11" }, "marcucci2016": { "key": "marcucci2016", "authors": "L. E. Marcucci, G. Mangano, A. Kievsky, M. Viviani", "title": "Implication of the proton-deuteron radiative capture for Big Bang Nucleosynthesis", "journal": "Phys. Rev. Lett. 116, 102501 (2016)", "year": 2016, "doi": "10.1103/PhysRevLett.116.102501", "arxiv": "1510.07877", "checked": "arXiv 1510.07877 and University of Pisa and Naples repository records; DOI from the APS scheme, 2026-10-11" }, "tisma2019": { "key": "tisma2019", "authors": "I. Tišma, M. Lipoglavšek, M. Mihovilovič et al.", "title": "Experimental cross section and angular distribution of the ²H(p,γ)³He reaction at Big-Bang nucleosynthesis energies", "journal": "Eur. Phys. J. A 55, 137 (2019)", "year": 2019, "doi": "10.1140/epja/i2019-12816-1", "checked": "Springer article page and INSPIRE record 1750911 as listed by search, 2026-10-11" }, "mossa2020b": { "key": "mossa2020b", "authors": "V. Mossa et al. (LUNA Collaboration)", "title": "Setup commissioning for an improved measurement of the D(p,γ)³He cross section at Big Bang Nucleosynthesis energies", "journal": "Eur. Phys. J. A 56, 144 (2020)", "year": 2020, "doi": "10.1140/epja/s10050-020-00149-1", "arxiv": "2005.00002", "luna": true, "checked": "arXiv 2005.00002 and HZDR publication record, 2026-10-11" }, "turkat2021": { "key": "turkat2021", "authors": "S. Turkat et al.", "title": "Measurement of the ²H(p,γ)³He S factor at 265–1094 keV", "journal": "Phys. Rev. C 103, 045805 (2021)", "year": 2021, "doi": "10.1103/PhysRevC.103.045805", "arxiv": "2104.06914", "checked": "arXiv 2104.06914, HZDR record Publ-31449 and JYX repository record; DOI from the APS scheme, 2026-10-11" }, "arpesella1996": { "key": "arpesella1996", "authors": "C. Arpesella et al. (LUNA Collaboration)", "title": "Measurement of the ³He(³He,2p)⁴He cross section within the solar Gamow peak", "journal": "Phys. Lett. B 389, 452 (1996)", "year": 1996, "luna": true, "checked": "ACNP index and Turin IRIS record (vol. 389, pp. 452–456); DOI not found, 2026-10-11" }, "junker1998": { "key": "junker1998", "authors": "M. Junker et al. (LUNA Collaboration)", "title": "Cross section of ³He(³He,2p)⁴He measured at solar energies", "journal": "Phys. Rev. C 57, 2700 (1998)", "year": 1998, "doi": "10.1103/PhysRevC.57.2700", "arxiv": "nucl-ex/9707003", "luna": true, "checked": "arXiv nucl-ex/9707003 journal reference and DOI, Turin IRIS abstract, 2026-10-11" }, "kudomi2004": { "key": "kudomi2004", "authors": "N. Kudomi, M. Komori, K. Takahisa, S. Yoshida, K. Kume, H. Ohsumi, T. Itahashi", "title": "Precise measurement of cross section of ³He(³He,2p)⁴He by using ³He doubly charged beam", "journal": "Phys. Rev. C 69, 015802 (2004)", "year": 2004, "doi": "10.1103/PhysRevC.69.015802", "arxiv": "astro-ph/0306454", "checked": "arXiv astro-ph/0306454 and EXFOR entry E1890; DOI from the APS scheme, 2026-10-11" }, "zylstra2017": { "key": "zylstra2017", "authors": "A. B. Zylstra et al.", "title": "Proton spectra from ³He+T and ³He+³He fusion at low center-of-mass energy, with potential implications for solar fusion cross sections", "journal": "Phys. Rev. Lett. 119, 222701 (2017)", "year": 2017, "doi": "10.1103/PhysRevLett.119.222701", "checked": "APS accepted-manuscript link and MIT DSpace record 1721.1/114497, 2026-10-11" }, "narasingh2004": { "key": "narasingh2004", "authors": "B. S. Nara Singh, M. Hass, Y. Nir-El, G. Haquin", "title": "New precision measurement of the ³He(⁴He,γ)⁷Be cross section", "journal": "Phys. Rev. Lett. 93, 262503 (2004)", "year": 2004, "doi": "10.1103/PhysRevLett.93.262503", "arxiv": "nucl-ex/0407017", "checked": "arXiv nucl-ex/0407017 and Ben-Gurion and UWS research-portal records with DOI, 2026-10-11" }, "bemmerer2006": { "key": "bemmerer2006", "authors": "D. Bemmerer et al. (LUNA Collaboration)", "title": "Activation measurement of the ³He(α,γ)⁷Be cross section at low energy", "journal": "Phys. Rev. Lett. 97, 122502 (2006)", "year": 2006, "doi": "10.1103/PhysRevLett.97.122502", "arxiv": "nucl-ex/0609013", "luna": true, "checked": "arXiv nucl-ex/0609013 and HZDR record Publ-10247; DOI from the APS scheme, 2026-10-11" }, "gyurky2007": { "key": "gyurky2007", "authors": "Gy. Gyürky et al. (LUNA Collaboration)", "title": "³He(α,γ)⁷Be cross section at low energies", "journal": "Phys. Rev. C 75, 035805 (2007)", "year": 2007, "doi": "10.1103/PhysRevC.75.035805", "luna": true, "checked": "University of Milan record and abstract quoted in later LUNA papers; DOI from the APS scheme, 2026-10-11" }, "confortola2007": { "key": "confortola2007", "authors": "F. Confortola et al. (LUNA Collaboration)", "title": "Astrophysical S factor of the ³He(α,γ)⁷Be reaction measured at low energy via detection of prompt and delayed γ rays", "journal": "Phys. Rev. C 75, 065803 (2007)", "year": 2007, "doi": "10.1103/PhysRevC.75.065803", "arxiv": "0705.2151", "luna": true, "checked": "arXiv 0705.2151, University of Milan and Turin records; DOI from the APS scheme, 2026-10-11" }, "brown2007": { "key": "brown2007", "authors": "T. A. D. Brown, C. Bordeanu, K. A. Snover et al.", "title": "³He + ⁴He → ⁷Be astrophysical S factor", "journal": "Phys. Rev. C 76, 055801 (2007)", "year": 2007, "doi": "10.1103/PhysRevC.76.055801", "arxiv": "0710.1279", "checked": "arXiv 0710.1279, Texas A&M publication list and EXFOR entry C1610, 2026-10-11" }, "costantini2008": { "key": "costantini2008", "authors": "H. Costantini et al. (LUNA Collaboration)", "title": "The ³He(α,γ)⁷Be S-factor at solar energies: the prompt γ experiment at LUNA", "journal": "Nucl. Phys. A 814, 144 (2008)", "year": 2008, "doi": "10.1016/j.nuclphysa.2008.09.014", "arxiv": "0809.5269", "luna": true, "checked": "arXiv 0809.5269 and HZDR record Publ-12003, 2026-10-11" }, "dileva2009": { "key": "dileva2009", "authors": "A. Di Leva et al.", "title": "Stellar and primordial nucleosynthesis of ⁷Be: measurement of ³He(α,γ)⁷Be", "journal": "Phys. Rev. Lett. 102, 232502 (2009); erratum Phys. Rev. Lett. 103 (2009)", "year": 2009, "doi": "10.1103/PhysRevLett.102.232502", "checked": "University of Naples IRIS record and JINA Virtual Journal listing of the article and its erratum; DOI from the APS scheme, 2026-10-11" }, "kontos2013": { "key": "kontos2013", "authors": "A. Kontos, E. Uberseder, R. deBoer, J. Görres, C. Akers, A. Best, M. Couder, M. Wiescher", "title": "Astrophysical S factor of ³He(α,γ)⁷Be", "journal": "Phys. Rev. C 87, 065804 (2013)", "year": 2013, "doi": "10.1103/PhysRevC.87.065804", "checked": "University of Naples IRIS record and later citations; DOI quoted there, 2026-10-11" }, "szucs2019": { "key": "szucs2019", "authors": "T. Szücs, G. G. Kiss, Gy. Gyürky, Z. Halász, T. N. Szegedi, Zs. Fülöp", "title": "Cross section of ³He(α,γ)⁷Be around the ⁷Be proton separation threshold", "journal": "Phys. Rev. C 99, 055804 (2019)", "year": 2019, "doi": "10.1103/PhysRevC.99.055804", "checked": "HZDR record Publ-29287 and REAL repository record 99555; DOI from the APS scheme, 2026-10-11" }, "filippone1983": { "key": "filippone1983", "authors": "B. W. Filippone, A. J. Elwyn, C. N. Davids, D. D. Koetke", "title": "Proton capture cross section of ⁷Be and the flux of high energy solar neutrinos", "journal": "Phys. Rev. C 28, 2222 (1983)", "year": 1983, "doi": "10.1103/PhysRevC.28.2222", "checked": "Caltech Authors record and EXFOR entry; DOI quoted in the bibliographic records, 2026-10-11" }, "hammache1998": { "key": "hammache1998", "authors": "F. Hammache et al.", "title": "New measurement and analysis of the ⁷Be(p,γ)⁸B cross section", "journal": "Phys. Rev. Lett. 80, 928 (1998)", "year": 1998, "doi": "10.1103/PhysRevLett.80.928", "arxiv": "nucl-ex/9712003", "checked": "arXiv nucl-ex/9712003 journal reference; DOI from the APS scheme, 2026-10-11" }, "hammache2001": { "key": "hammache2001", "authors": "F. Hammache et al.", "title": "Low-energy measurement of the ⁷Be(p,γ)⁸B cross section", "journal": "Phys. Rev. Lett. 86, 3985 (2001)", "year": 2001, "doi": "10.1103/PhysRevLett.86.3985", "arxiv": "nucl-ex/0101014", "checked": "arXiv nucl-ex/0101014, UCLouvain and Bordeaux repository records with DOI, 2026-10-11" }, "baby2003": { "key": "baby2003", "authors": "L. T. Baby, M. Hass et al.", "title": "Precision measurement of the ⁷Be(p,γ)⁸B cross section with an implanted ⁷Be target", "journal": "Phys. Rev. Lett. 90, 022501 (2003); erratum Phys. Rev. Lett. 92, 029901 (2004)", "year": 2003, "doi": "10.1103/PhysRevLett.90.022501", "arxiv": "nucl-ex/0208005", "checked": "arXiv nucl-ex/0208005 journal reference and Weizmann research-portal record; DOI from the APS scheme; author list beyond Baby and Hass not seen on the publisher page, 2026-10-11" }, "junghans2003": { "key": "junghans2003", "authors": "A. R. Junghans et al.", "title": "Precise measurement of the ⁷Be(p,γ)⁸B S factor", "journal": "Phys. Rev. C 68, 065803 (2003)", "year": 2003, "doi": "10.1103/PhysRevC.68.065803", "arxiv": "nucl-ex/0308003", "checked": "HZDR record Publ-6536 and arXiv nucl-ex/0308003; DOI from the APS scheme, 2026-10-11" }, "junghans2010": { "key": "junghans2010", "authors": "A. R. Junghans, K. A. Snover, E. C. Mohrmann, E. G. Adelberger, L. Buchmann", "title": "Updated S factors for the ⁷Be(p,γ)⁸B reaction", "journal": "Phys. Rev. C 81, 012801(R) (2010)", "year": 2010, "doi": "10.1103/PhysRevC.81.012801", "checked": "HZDR record Publ-13139 and JINA Virtual Journal listing (5 March 2010); DOI from the APS scheme, 2026-10-11" }, "motobayashi1994": { "key": "motobayashi1994", "authors": "T. Motobayashi et al.", "title": "Coulomb dissociation of ⁸B and the ⁷Be(p,γ)⁸B reaction at low energies", "journal": "Phys. Rev. Lett. 73, 2680 (1994)", "year": 1994, "doi": "10.1103/PhysRevLett.73.2680", "checked": "EXFOR entry E1576 (journal reference and title); DOI from the APS scheme, 2026-10-11" }, "schumann2003": { "key": "schumann2003", "authors": "F. Schümann, F. Hammache, S. Typel et al.", "title": "Coulomb dissociation of ⁸B and the low-energy cross section of the ⁷Be(p,γ)⁸B solar fusion reaction", "journal": "Phys. Rev. Lett. 90, 232501 (2003)", "year": 2003, "doi": "10.1103/PhysRevLett.90.232501", "arxiv": "nucl-ex/0304011", "checked": "Santiago de Compostela research-portal record (volume, issue, year) and arXiv nucl-ex/0304011; DOI from the APS scheme, 2026-10-11" }, "schumann2006": { "key": "schumann2006", "authors": "F. Schümann, S. Typel et al.", "title": "Low-energy cross section of the ⁷Be(p,γ)⁸B solar fusion reaction from the Coulomb dissociation of ⁸B", "journal": "Phys. Rev. C 73, 015806 (2006)", "year": 2006, "doi": "10.1103/PhysRevC.73.015806", "checked": "Santiago de Compostela research-portal record with DOI, 2026-10-11" }, "kiener1991": { "key": "kiener1991", "authors": "J. Kiener, H. J. Gils, H. Rebel, S. Zagromski, G. Gsottschneider, N. Heide, H. Jelitto, J. Wentz, G. Baur", "title": "Measurements of the Coulomb dissociation cross section of 156 MeV ⁶Li projectiles at extremely low relative fragment energies of astrophysical interest", "journal": "Phys. Rev. C 44, 2195 (1991)", "year": 1991, "doi": "10.1103/PhysRevC.44.2195", "checked": "KIT library record (also KfK report 4870) and later citations; DOI from the APS scheme, 2026-10-11" }, "hammache2010": { "key": "hammache2010", "authors": "F. Hammache et al.", "title": "High-energy breakup of ⁶Li as a tool to study the Big Bang nucleosynthesis reaction ²H(α,γ)⁶Li", "journal": "Phys. Rev. C 82, 065803 (2010)", "year": 2010, "doi": "10.1103/PhysRevC.82.065803", "arxiv": "1011.6179", "checked": "Santiago de Compostela research-portal record with DOI, HZDR record Publ-14337 and arXiv 1011.6179, 2026-10-11" }, "anders2014": { "key": "anders2014", "authors": "M. Anders et al. (LUNA Collaboration)", "title": "First direct measurement of the ²H(α,γ)⁶Li cross section at Big Bang energies and the primordial lithium problem", "journal": "Phys. Rev. Lett. 113, 042501 (2014)", "year": 2014, "doi": "10.1103/PhysRevLett.113.042501", "luna": true, "checked": "HZDR record Publ-19877, Edinburgh, Milan and Turin repository records with DOI, 2026-10-11" }, "trezzi2017": { "key": "trezzi2017", "authors": "D. Trezzi et al. (LUNA Collaboration)", "title": "Big Bang ⁶Li nucleosynthesis studied deep underground (LUNA collaboration)", "journal": "Astropart. Phys. 89, 57 (2017)", "year": 2017, "doi": "10.1016/j.astropartphys.2017.01.007", "luna": true, "checked": "HZDR record Publ-25241, Edinburgh and Milan repository records with DOI; last page differs between repositories, 2026-10-11" }, "costantini2000": { "key": "costantini2000", "authors": "H. Costantini et al. (LUNA Collaboration)", "title": "Stopping power, electron screening and the astrophysical S(E) factor of d(³He,p)⁴He", "journal": "Phys. Lett. B 482, 43 (2000)", "year": 2000, "doi": "10.1016/S0370-2693(00)00513-X", "luna": true, "checked": "Naples, Pisa and Turin repository records (pp. 43–49) with DOI, 2026-10-11" }, "aliotta2001": { "key": "aliotta2001", "authors": "M. Aliotta, F. Raiola, G. Gyürky et al.", "title": "Electron screening effect in the reactions ³He(d,p)⁴He and d(³He,p)⁴He", "journal": "Nucl. Phys. A 690, 790 (2001)", "year": 2001, "doi": "10.1016/S0375-9474(01)00366-9", "checked": "EXFOR entry A0228 and Naples IRIS record with DOI, 2026-10-11" }, "lacognata2005": { "key": "lacognata2005", "authors": "M. La Cognata et al.", "title": "Bare-nucleus astrophysical factor of the ³He(d,p)⁴He reaction via the \"Trojan horse\" method", "journal": "Phys. Rev. C 72 (2005), issue 6", "year": 2005, "checked": "JINA Virtual Journal listing (Phys. Rev. C 72, issue 6), OSTI and Catania IRIS records of the abstract, citation as \"La Cognata et al. 2005\" in arXiv 1403.4909; article number, full author list and DOI not confirmed, 2026-10-11" }, "koehler1988": { "key": "koehler1988", "authors": "P. E. Koehler, C. D. Bowman et al.", "title": "⁷Be(n,p)⁷Li total cross section from 25 meV to 13.5 keV", "journal": "Phys. Rev. C 37, 917 (1988)", "year": 1988, "doi": "10.1103/PhysRevC.37.917", "checked": "APS issue listing (vol. 37, no. 3) and later reviews; DOI from the APS scheme, 2026-10-11" }, "damone2018": { "key": "damone2018", "authors": "L. Damone et al. (n_TOF Collaboration)", "title": "⁷Be(n,p)⁷Li reaction and the cosmological lithium problem", "journal": "Phys. Rev. Lett. 121, 042701 (2018)", "year": 2018, "doi": "10.1103/PhysRevLett.121.042701", "arxiv": "1806.03050", "checked": "Seville, INAF, Manchester and White Rose repository records with DOI, 2026-10-11; arXiv number rechecked by web search (1803.05701 withdrawn as a duplicate of 1806.03050), 2026-10-13" }, "schiavilla1998": { "key": "schiavilla1998", "authors": "R. Schiavilla, V. G. J. Stoks et al.", "title": "Weak capture of protons by protons", "journal": "Phys. Rev. C 58, 1263 (1998)", "year": 1998, "doi": "10.1103/PhysRevC.58.1263", "arxiv": "nucl-th/9808010", "checked": "arXiv nucl-th/9808010 and Adelaide repository record (pp. 1263–1277) with DOI, 2026-10-11" }, "marcucci2013": { "key": "marcucci2013", "authors": "L. E. Marcucci, R. Schiavilla, M. Viviani", "title": "Proton-proton weak capture in chiral effective field theory", "journal": "Phys. Rev. Lett. 110, 192503 (2013); erratum Phys. Rev. Lett. 123, 019901 (2019)", "year": 2013, "doi": "10.1103/PhysRevLett.110.192503", "arxiv": "1303.3124", "checked": "APS DOI link in search results, arXiv 1303.3124 and Pisa repository record; erratum as cited in later work, 2026-10-11" }, "marcucci2000": { "key": "marcucci2000", "authors": "L. E. Marcucci, R. Schiavilla, M. Viviani, A. Kievsky, S. Rosati, J. F. Beacom", "title": "Weak proton capture on ³He", "journal": "Phys. Rev. C 63, 015801 (2000)", "year": 2000, "doi": "10.1103/PhysRevC.63.015801", "arxiv": "nucl-th/0006005", "checked": "arXiv nucl-th/0006005 journal reference and Pisa repository record; DOI from the APS scheme, 2026-10-11" }, "aharmim2006": { "key": "aharmim2006", "authors": "B. Aharmim et al. (SNO Collaboration)", "title": "A search for neutrinos from the solar hep reaction and the diffuse supernova neutrino background with the Sudbury Neutrino Observatory", "journal": "Astrophys. J. 653, 1545 (2006)", "year": 2006, "arxiv": "hep-ex/0607010", "checked": "arXiv hep-ex/0607010, SNO collaboration paper list and Kentucky and IP Paris research-portal records (pp. 1545–1551); DOI not seen, 2026-10-11" }, "borexino2012": { "key": "borexino2012", "authors": "G. Bellini et al. (Borexino Collaboration)", "title": "First evidence of pep solar neutrinos by direct detection in Borexino", "journal": "Phys. Rev. Lett. 108, 051302 (2012)", "year": 2012, "doi": "10.1103/PhysRevLett.108.051302", "arxiv": "1110.3230", "checked": "arXiv 1110.3230, Princeton and Perugia repository records; DOI from the APS scheme, 2026-10-11" }, "rupak2000": { "key": "rupak2000", "authors": "G. Rupak", "title": "Precision calculation of np → dγ cross section for big-bang nucleosynthesis", "journal": "Nucl. Phys. A 678, 405 (2000)", "year": 2000, "doi": "10.1016/S0375-9474(00)00323-7", "arxiv": "nucl-th/9911018", "checked": "arXiv nucl-th/9911018, which links the DOI; volume and page not seen on the publisher page, 2026-10-11" }, "greife1995": { "key": "greife1995", "authors": "U. Greife, F. Gorris, M. Junker, C. Rolfs, D. Zahnow", "title": "Oppenheimer-Phillips effect and electron screening in d+d fusion reactions", "journal": "Z. Phys. A 351, 107 (1995)", "year": 1995, "doi": "10.1007/BF01292792", "checked": "Springer DOI page with abstract and EXFOR entry O1171, 2026-10-11" }, "leonard2006": { "key": "leonard2006", "authors": "D. S. Leonard, H. J. Karwowski, C. R. Brune, B. M. Fisher, E. J. Ludwig", "title": "Precision measurements of ²H(d,p)³H and ²H(d,n)³He total cross sections at Big Bang nucleosynthesis energies", "journal": "Phys. Rev. C 73, 045801 (2006)", "year": 2006, "doi": "10.1103/PhysRevC.73.045801", "arxiv": "nucl-ex/0601035", "checked": "arXiv nucl-ex/0601035 and EXFOR entry C1499; DOI from the APS scheme, 2026-10-11" }, "tumino2014": { "key": "tumino2014", "authors": "A. Tumino et al.", "title": "New determination of the ²H(d,p)³H and ²H(d,n)³He reaction rates at astrophysical energies", "journal": "Astrophys. J. 785, 96 (2014)", "year": 2014, "checked": "Texas A&M Cyclotron Institute publication list and later THM reviews; DOI not seen, 2026-10-11" }, "bosch1992": { "key": "bosch1992", "authors": "H.-S. Bosch, G. M. Hale", "title": "Improved formulas for fusion cross-sections and thermal reactivities", "journal": "Nucl. Fusion 32, 611 (1992); correction Nucl. Fusion 33, 1919 (1993)", "year": 1992, "checked": "INIS record (vol. 32, no. 4, pp. 611–631) and IOP page of the 1993 correction; DOI of the 1992 article not seen, 2026-10-11" }, "brune1994": { "key": "brune1994", "authors": "C. R. Brune, R. W. Kavanagh, C. Rolfs", "title": "³H(α,γ)⁷Li reaction at low energies", "journal": "Phys. Rev. C 50, 2205 (1994)", "year": 1994, "doi": "10.1103/PhysRevC.50.2205", "checked": "Caltech Authors feed, Caltech thesis record 6174 and EXFOR entry C0191; DOI from the APS scheme, 2026-10-11" }, "engstler1992": { "key": "engstler1992", "authors": "S. Engstler, G. Raimann, C. Angulo, U. Greife, C. Rolfs, U. Schröder, E. Somorjai, B. Kirch, K. Langanke", "title": "Isotopic dependence of electron screening in fusion reactions", "journal": "Z. Phys. A 342, 471 (1992)", "year": 1992, "doi": "10.1007/BF01294958", "checked": "EXFOR entry A0632 and Atomki publication database; DOI from a doi.org page carrying the abstract, 2026-10-11" }, "lattuada2001": { "key": "lattuada2001", "authors": "M. Lattuada, R. G. Pizzone, S. Typel et al.", "title": "The bare astrophysical S(E) factor of the ⁷Li(p,α)α reaction", "journal": "Astrophys. J. 562, 1076 (2001)", "year": 2001, "checked": "full text in the Catania IRIS repository (pp. 1076–1080); DOI not seen, 2026-10-11" }, "chen2025": { "key": "chen2025", "authors": "X. Chen, J. Su, Y. P. Shen et al.", "title": "Enhanced S-factor for the ¹⁴N(p,γ)¹⁵O reaction and its impact on the solar composition problem", "journal": "Phys. Rev. Lett. 135, 232701 (2025)", "year": 2025, "doi": "10.1103/q756-hzmt", "arxiv": "2410.16086", "checked": "Nature Index record (PRL 135, 232701, 2 December 2025, DOI) and arXiv 2410.16086 snippets (direct measurement at Ep = 110–260 keV with the 350 kV accelerator in Hefei, all transitions fitted together in a multichannel Bayesian analysis), by web search; S(0) = 1.92 ± 0.08 keV b (about 14% above Solar Fusion III's 1.68 keV b) verified by the owner, 2026-10-13" }, "borexino2023": { "key": "borexino2023", "authors": "D. Basilico et al. (Borexino Collaboration)", "title": "Final results of Borexino on CNO solar neutrinos", "journal": "Phys. Rev. D 108, 102005 (2023)", "year": 2023, "arxiv": "2307.14636", "checked": "arXiv 2307.14636 abstract and the Princeton, TUM and TU Dresden records, by web search (φ_CNO = 6.7 +1.2/−0.8 × 10⁸ cm⁻² s⁻¹; with ⁷Be and ⁸B, B16-AGSS09met disfavoured at 3.2σ assuming B16-GS98; N_CN = 5.81 +1.22/−0.94 × 10⁻⁴, 2σ from the low-metallicity case; published 14 November 2023); DOI not shown, 2026-10-13" }, "asplund2021": { "key": "asplund2021", "authors": "M. Asplund, A. M. Amarsi, N. Grevesse", "title": "The chemical make-up of the Sun: A 2020 vision", "journal": "Astron. Astrophys. 653, A141 (2021)", "year": 2021, "arxiv": "2105.01661", "checked": "arXiv 2105.01661 and ANU record (Z = 0.0139; the solar modelling problem \"remains intact\"; journal reference A&A 653, A141), by web search, 2026-10-13" }, "magg2022": { "key": "magg2022", "authors": "E. Magg et al.", "title": "Observational constraints on the origin of the elements. IV. Standard composition of the Sun", "journal": "Astron. Astrophys. 661, A140 (2022)", "year": 2022, "doi": "10.1051/0004-6361/202142971", "arxiv": "2203.02255", "checked": "A&A article page and arXiv 2203.02255 (Z/X = 0.0225; the mismatch with helioseismology resolved with this composition), by web search, 2026-10-13" }, "iliadis2022": { "key": "iliadis2022", "authors": "C. Iliadis, V. Palanivelrajan, R. S. de Souza", "title": "Bayesian estimation of the S factor and thermonuclear reaction rate for ¹⁶O(p,γ)¹⁷F", "journal": "Phys. Rev. C 106, 055802 (2022)", "year": 2022, "doi": "10.1103/PhysRevC.106.055802", "arxiv": "2210.14354", "checked": "arXiv 2210.14354 abstract and University of Hertfordshire record, by web search (potential model with the ANCs as scaling parameters; rate uncertainty ±4.2%, about half of the earlier 7.5%); DOI from the APS scheme, 2026-10-13" }, "toth2023": { "key": "toth2023", "authors": "Á. Tóth, T. Szücs et al.", "title": "Experimental determination of the ³He(α,γ)⁷Be reaction cross section above the ⁷Be proton separation threshold", "journal": "Phys. Rev. C 108, 025802 (2023)", "year": 2023, "doi": "10.1103/PhysRevC.108.025802", "arxiv": "2307.10218", "checked": "EXFOR entry D4430 (journal reference and DOI) and arXiv 2307.10218, by web search (activation with a ³He gas cell; extends the data above the proton threshold, where only one data set at 4.0–4.4 MeV existed), 2026-10-13" }, "hayakawa2021": { "key": "hayakawa2021", "authors": "S. Hayakawa, M. La Cognata, L. Lamia et al.", "title": "Constraining the primordial lithium abundance: new cross section measurement of the ⁷Be + n reactions updates the total ⁷Be destruction rate", "journal": "Astrophys. J. Lett. 915, L13 (2021)", "year": 2021, "doi": "10.3847/2041-8213/ac061f", "checked": "conference abstracts of the same group and the CRIB report, by web search (Trojan Horse ⁷Be(d,⁷Li p)¹H and ⁷Be(d,αα)¹H with a CRIB beam; improved (n,p₀), first (n,p₁) at BBN energies; about 10% less ⁷Li in PRIMAT), 2026-10-13" }, "guardo2023": { "key": "guardo2023", "authors": "G. L. Guardo et al.", "title": "Direct measurement of the ¹⁹F(p,α)¹⁶O reaction at E_cm = 0.4–0.9 MeV using the LHASA detector array", "journal": "Eur. Phys. J. A 59 (2023)", "year": 2023, "doi": "10.1140/epja/s10050-023-00957-1", "checked": "DOAJ and Osmangazi University records (EPJ A 59, issue 3; S-factor about 1.4 times NACRE at 0.6–0.8 MeV), by web search; article number not seen, 2026-10-13" }, "petruse2025": { "key": "petruse2025", "authors": "T. Petruse et al.", "title": "Direct measurement of the ¹⁹F(p,α)¹⁶O reaction using the LHASA detector array", "journal": "Eur. Phys. J. A 61, 4 (2025)", "year": 2025, "doi": "10.1140/epja/s10050-024-01462-9", "checked": "web-search records of the article (EPJ A 61, issue 1, DOI; E_cm = 400–900 keV; resolves the discrepancy between the two earlier data sets; INSPIRE copy of the article header, title), 2026-10-13" }, "pitrou2021": { "key": "pitrou2021", "authors": "C. Pitrou, A. Coc, J.-P. Uzan, E. Vangioni", "title": "A new tension in the cosmological model from primordial deuterium?", "journal": "Mon. Not. R. Astron. Soc. 502, 2474 (2021)", "year": 2021, "arxiv": "2011.11320", "checked": "arXiv 2011.11320 abstract (a 1.8σ tension on the baryon density, or on D/H, between BBN and CMB + BAO), by web search, 2026-10-13" }, "desouza2019": { "key": "desouza2019", "authors": "R. S. de Souza, C. Iliadis, A. Coc", "title": "Astrophysical S-factors, thermonuclear rates, and electron screening potential for the ³He(d,p)⁴He Big Bang reaction via a hierarchical Bayesian model", "journal": "Astrophys. J. (2019)", "year": 2019, "arxiv": "1809.06966", "checked": "arXiv 1809.06966 (journal ApJ; screening potential 213 ± 13 eV, consistent with Aliotta et al. 2001), by web search; volume and page not seen, 2026-10-13" }, "adsley2022": { "key": "adsley2022", "authors": "P. Adsley et al.", "title": "Extending the Hoyle-state paradigm to ¹²C + ¹²C fusion", "journal": "Phys. Rev. Lett. 129, 102701 (2022)", "year": 2022, "doi": "10.1103/PhysRevLett.129.102701", "checked": "University of the Western Cape and White Rose records, by web search (0⁺ states of ²⁴Mg near the ¹²C + ¹²C threshold from ²⁴Mg(α,α′), decaying mostly to ²⁰Ne + α; proposed cluster states that could enhance fusion), 2026-10-13" }, "dellaquila2024": { "key": "dellaquila2024", "authors": "D. Dell'Aquila et al.", "title": "Clarifying the radiative decay of the Hoyle state with charged-particle spectroscopy", "journal": "Sci. Rep. 14 (2024)", "year": 2024, "doi": "10.1038/s41598-024-68415-6", "arxiv": "2401.18026", "checked": "DOAJ record (Scientific Reports, August 2024) and arXiv 2401.18026, by web search (Γrad/Γ = 4.4(6) × 10⁻⁴; arXiv and journal versions may differ); article number not seen, 2026-10-13" }, "ogata2009": { "key": "ogata2009", "authors": "K. Ogata, M. Kan, M. Kamimura", "title": "Quantum three-body calculation of the nonresonant triple-α reaction rate at low temperatures", "journal": "Prog. Theor. Phys. 122, 1055 (2009)", "year": 2009, "arxiv": "0905.0007", "checked": "arXiv 0905.0007 (CDCC; about 20 orders of magnitude above NACRE near 10⁷ K) and a Tsukuba lecture citing the journal, by web search; the arXiv record gives the year as 2010, 2026-10-13" }, "nguyen2012": { "key": "nguyen2012", "authors": "N. B. Nguyen, F. M. Nunes, I. J. Thompson, E. F. Brown", "title": "Low-temperature triple-alpha rate in a full three-body model", "journal": "Phys. Rev. Lett. 109, 141101 (2012)", "year": 2012, "arxiv": "1112.2136", "checked": "JINA Virtual Journal listing (PRL 109, 141101) and arXiv 1112.2136 (agrees with NACRE above 0.07 GK; about 10¹² larger at 0.02 GK; red giants unaffected in MESA), by web search, 2026-10-13" }, "shen2023": { "key": "shen2023", "authors": "Y. P. Shen et al.", "title": "New determination of the ¹²C(α,γ)¹⁶O reaction rate and its impact on the black-hole mass gap", "journal": "Astrophys. J. 945, 41 (2023)", "year": 2023, "doi": "10.3847/1538-4357/acb7de", "checked": "ApJ article page, NSF PAR and DOAJ records, by web search (ground-state ANC from ¹²C(¹¹B,⁷Li)¹⁶O at the Q3D spectrograph; total rate up to 21% above deBoer et al. 2017; lower and upper edges of the black-hole gap down by about 12% and 5%), 2026-10-13" }, "haverson2026": { "key": "haverson2026", "authors": "K. Haverson, R. Smith, M. Gai et al.", "title": "Background-free ¹²C(α,γ) angular distribution measurements with a time projection chamber operating in gamma beams", "journal": "Commun. Phys. 9, 27 (2026)", "year": 2026, "doi": "10.1038/s42005-025-02458-7", "checked": "Communications Physics record (6 January 2026, DOI) and a 2026 LBL conference abstract, by web search (¹⁶O(γ,α) with an N₂O gas target at HIγS; E1–E2 phase angle reported to agree with unitarity for the first time); the value of the phase needs the full text, 2026-10-13" }, "farmer2020": { "key": "farmer2020", "authors": "R. Farmer, M. Renzo, S. E. de Mink, M. Fishbach, S. Justham", "title": "Constraints from gravitational-wave detections of binary black hole mergers on the ¹²C(α,γ)¹⁶O rate", "journal": "Astrophys. J. Lett. 902, L36 (2020)", "year": 2020, "arxiv": "2006.06678", "checked": "arXiv 2006.06678 and University of Amsterdam record, by web search (S(300 keV) > 175 keV b at 68% from the first ten black-hole mergers; O(50) mergers could pin S to ±10–30 keV b), 2026-10-13" }, "deboer2024": { "key": "deboer2024", "authors": "R. J. deBoer et al.", "title": "Measurement of the ¹³C(α,n₀)¹⁶O differential cross section from 0.8 to 6.5 MeV", "journal": "Phys. Rev. Lett. 132, 062702 (2024)", "year": 2024, "doi": "10.1103/PhysRevLett.132.062702", "checked": "ORNL record and NSF PAR copy, by web search (18 angles, 0–160°, over 700 angular distributions; extrapolation uncertainty potentially about 5%, against about 15% before; published 9 February 2024), 2026-10-13" }, "shahina2024": { "key": "shahina2024", "authors": "Shahina, R. J. deBoer, M. Wiescher et al.", "title": "Strength measurement of the E_α,lab = 830 keV resonance in the ²²Ne(α,n)²⁵Mg reaction using a stilbene detector", "journal": "Phys. Rev. C 110, 015801 (2024)", "year": 2024, "doi": "10.1103/PhysRevC.110.015801", "checked": "ORNL and AFIT records and the Notre Dame highlight, by web search (published 3 July 2024; (α,n) strength similar to earlier direct studies, about three times the (α,γ) strength, against transfer data that suggest the two are about equal), 2026-10-13" }, "tessler2021": { "key": "tessler2021", "authors": "M. Tessler, M. Paul et al.", "title": "Stellar s-process neutron capture cross sections on ⁷⁸,⁸⁰,⁸⁴,⁸⁶Kr determined via activation, atom trap trace analysis, and decay counting", "journal": "Phys. Rev. C 104, 015806 (2021)", "year": 2021, "doi": "10.1103/PhysRevC.104.015806", "checked": "APS accepted-manuscript link and Hebrew University and INAF records, by web search (SARAF-LiLiT activation; ⁸¹Kr and ⁸⁵ᵍKr counted by ATTA); its partial cross section to ⁸⁵Krᵐ underlies a branching to the isomer of about 0.59 used in arXiv 2107.12037, 2026-10-13" }, "lugaro2023": { "key": "lugaro2023", "authors": "M. Lugaro, M. Pignatari, R. Reifarth, M. Wiescher", "title": "The s process and beyond", "journal": "Annu. Rev. Nucl. Part. Sci. 73, 315 (2023)", "year": 2023, "doi": "10.1146/annurev-nucl-102422-080857", "arxiv": "2511.06987", "checked": "Annual Reviews record (pp. 315–340, 2 August 2023, CC BY 4.0) and arXiv 2511.06987, by web search, 2026-10-13" }, "vescovi2020": { "key": "vescovi2020", "authors": "D. Vescovi, S. Cristallo, M. Busso, N. Liu", "title": "Magnetic-buoyancy-induced mixing in AGB stars: presolar SiC grains", "journal": "Astrophys. J. Lett. 897, L25 (2020)", "year": 2020, "doi": "10.3847/2041-8213/ab9fa1", "arxiv": "2006.13729", "checked": "arXiv 2006.13729 and INAF record, by web search (ApJL 897, L25; FRUITY models with mixing triggered by magnetic buoyancy fit the Ni, Sr, Zr, Mo and Ba isotope ratios of mainstream SiC grains with one field configuration), 2026-10-13" }, "vescovi2023": { "key": "vescovi2023", "authors": "D. Vescovi, R. Reifarth, E. Lorenz, A. Elbe", "title": "The ASTRAL database for neutron-capture nucleosynthesis studies", "journal": "EPJ Web Conf. 279, 11011 (2023)", "year": 2023, "doi": "10.1051/epjconf/202327911011", "checked": "EPJ Web of Conferences page and Frankfurt repository copy, by web search (MACS recalculated from the raw data with updated half-lives and γ intensities; successor of KADoNiS, whose version 1.0 was never released, per R. Reifarth's 2021 IAEA report), 2026-10-13" }, "leckenby2024": { "key": "leckenby2024", "authors": "G. Leckenby et al.", "title": "High-temperature ²⁰⁵Tl decay clarifies ²⁰⁵Pb dating in early Solar System", "journal": "Nature 635, 321 (2024)", "year": 2024, "doi": "10.1038/s41586-024-08130-4", "arxiv": "2411.08856", "checked": "MPI-K and TRIUMF press releases, the Zenodo record of the analysis and the ORIGINS news item, by web search (bound-state β decay of bare ²⁰⁵Tl⁸¹⁺ in the GSI storage ring, half-life 291 +33/−27 days; longer than the earlier theoretical estimate, by 4.7 times in the GSI record and the ORIGINS news but twice in the MPI-K press release, so no factor is quoted; feeds the ²⁰⁵Pb chronometer); title, pages 321–326 and arXiv 2411.08856 from the GSI repository record, 2026-10-13" }, "bosch1996": { "key": "bosch1996", "authors": "F. Bosch et al.", "title": "Observation of bound-state β⁻ decay of fully ionized ¹⁸⁷Re: ¹⁸⁷Re–¹⁸⁷Os cosmochronometry", "journal": "Phys. Rev. Lett. 77, 5190 (1996)", "year": 1996, "doi": "10.1103/PhysRevLett.77.5190", "checked": "GSI repository and OSTI records, and the ENSDF evaluation, by web search (half-life of bare ¹⁸⁷Re 32.9 ± 2.0 yr against about 42 Gyr for the neutral atom), 2026-10-13" }, "lerendegui2023": { "key": "lerendegui2023", "authors": "J. Lerendegui-Marco", "title": "Recent developments and perspectives for key stellar (n,γ) measurements at the CERN n_TOF facility", "journal": "Conference talk, Madrid, 2–6 October 2023", "year": 2023, "url": "https://indico.cern.ch/event/1283224/contributions/5585039", "checked": "Indico contribution page (results of the first measurement of the s-process branching-point reaction ⁷⁹Se(n,γ)), the 2020 n_TOF proposal (3 mg of ⁷⁹Se in a PbSe sample; i-TED) and the CERN EP newsletter item (EAR1 and EAR2; key to the s-only ⁸⁰Kr and ⁸²Kr), by web search; no journal article yet, 2026-10-13" }, "mukhamedzhanov2024": { "key": "mukhamedzhanov2024", "authors": "A. M. Mukhamedzhanov, R. J. deBoer et al.", "title": "Asymptotic normalization coefficients for α + ¹²C synthesis and the S factor for ¹²C(α,γ)¹⁶O radiative capture", "journal": "Phys. Rev. C 110, 055803 (2024)", "year": 2024, "doi": "10.1103/PhysRevC.110.055803", "checked": "published record and the Texas A&M Cyclotron Institute progress report 2023–2024, by web search (R-matrix fits with AZURE2; with their larger subthreshold ANCs the total S(300 keV) is 174 keV b, against 137 keV b in deBoer et al. 2017), 2026-10-13" }, "herwig2000": { "key": "herwig2000", "authors": "F. Herwig, N. Langer", "title": "Formation of the neutron donor ¹³C in AGB stars by overshoot and rotation", "journal": "Mem. Soc. Astron. Ital. (invited talk, Torino–Melbourne–Pasadena workshop)", "year": 2000, "arxiv": "astro-ph/0007390", "checked": "arXiv astro-ph/0007390 listing and the Potsdam abstract page, by web search (exponentially decaying overshoot during third dredge-up forms the pocket; rotation keeps mixing it during the interpulse); volume and page not seen, 2026-10-13" }, "choplin2022": { "key": "choplin2022", "authors": "A. Choplin, L. Siess, S. Goriely", "title": "The intermediate neutron capture process. III. The i-process in AGB stars of different masses and metallicities without overshoot", "journal": "Astron. Astrophys. 667, A155 (2022)", "year": 2022, "doi": "10.1051/0004-6361/202244360", "arxiv": "2209.10303", "checked": "arXiv 2209.10303 (proton ingestion events; \"the astrophysical site of the i-process is still a matter of debate\"; low-mass, low-metallicity AGB stars as candidates) and the A&A record (volume 667, A155, 22 November 2022, DOI), by web search, 2026-10-13" }, "rapagnani2025": { "key": "rapagnani2025", "authors": "D. Rapagnani et al. (LUNA Collaboration)", "title": "Revision of the CNO cycle: rate of ¹⁷O destruction in stars", "journal": "Phys. Rev. C 111, 025805 (2025)", "year": 2025, "doi": "10.1103/PhysRevC.111.025805", "luna": true, "checked": "University of Edinburgh Research Explorer, Genova and Padova IRIS records, by web search (Phys. Rev. C 111, issue 2, 2025; R-matrix fits with Monte Carlo uncertainties for ¹⁷O(p,γ)¹⁸F and ¹⁷O(p,α)¹⁴N; below about 100 MK the median rates are up to a factor of 2 above the rate libraries used in stellar models; ¹⁷O is destroyed mainly by (p,α), whose rate is known within ±20% at 95% C.L.); article number and DOI from content/publications.yaml; first author D. Rapagnani (then Straniero, Imbriani, Aliotta) confirmed by the INSPIRE record 2893094 in the lit2 fact-check, 2026-10-13" }, "skowronski2025b": { "key": "skowronski2025b", "authors": "J. Skowronski et al. (LUNA Collaboration)", "title": "A comparative analysis of R-matrix fitting: ¹²C(p,γ)¹³N as test case", "journal": "Phys. Rev. C 111, 035802 (2025)", "year": 2025, "doi": "10.1103/PhysRevC.111.035802", "arxiv": "2502.14040", "luna": true, "checked": "arXiv 2502.14040 abstract and Padova, Naples and Genova IRIS records, by web search (frequentist and Bayesian R-matrix methods compared on the same ¹²C(p,γ) data; the treatment of systematic uncertainties and the estimate of the covariance matrix are what make the uncertainties reliable and reproducible), 2026-10-13" }, "stockel2024": { "key": "stockel2024", "authors": "K. Stöckel et al. (LUNA Collaboration)", "title": "Novel approach to infer the ²H(p,γ)³He angular distribution: experimental results and comparison with theoretical calculations", "journal": "Phys. Rev. C 110, L032801 (2024)", "year": 2024, "doi": "10.1103/PhysRevC.110.L032801", "luna": true, "checked": "JINA Virtual Journal listing of 20 September 2024 (journal and DOI) and the Genova IRIS record, by web search (angular distribution inferred from the shape of the γ spectra of one HPGe detector facing an extended D₂ gas target at Gran Sasso, 30–280 keV, compared with ab initio predictions), 2026-10-13" }, "deboer2025": { "key": "deboer2025", "authors": "R. J. deBoer et al.", "title": "Total cross section of ¹⁴N + n from 0.1 to 12 MeV", "journal": "Phys. Rev. C 112, 025805 (2025)", "year": 2025, "doi": "10.1103/frgb-j5c3", "arxiv": "2505.04995", "checked": "APS abstract page, arXiv 2505.04995, TU Dresden record and RODARE data record 3977, by web search (published 20 August 2025; time-of-flight transmission at nELBE, HZDR; only one earlier high-sensitivity total cross section; good agreement with earlier data except at the lowest resonance, E_n = 433 keV; ¹⁴N(n,p) matters as an s-process neutron poison and for estimates of the \"yields of atmospheric nuclear weapon testing\", in the abstract's words; the abstract does not say fission, r16 fact-check), 2026-10-13" }, "wang2023": { "key": "wang2023", "authors": "L. H. Wang, J. Su et al. (JUNA Collaboration)", "title": "Measurement of the ¹⁸O(α,γ)²²Ne reaction rate at JUNA and its impact on probing the origin of SiC grains", "journal": "Phys. Rev. Lett. 130, 092701 (2023)", "year": 2023, "doi": "10.1103/PhysRevLett.130.092701", "checked": "APS abstract page, JINA Virtual Journal listing and NSR entry 2023WA05, by web search (E_α = 470–787 keV; key resonance at E_α = 474.0 ± 1.1 keV, measured this precisely for the first time; Jπ = 1⁻ from the primary γ branchings, removing the discrepancies between earlier strengths; rate up to about 10 times more precise at 0.1–0.3 GK), 2026-10-13" }, "kajino2023": { "key": "kajino2023", "authors": "T. Kajino", "title": "Underground laboratory JUNA shedding light on stellar nucleosynthesis", "journal": "Nucl. Sci. Tech. 34 (2023)", "year": 2023, "doi": "10.1007/s41365-023-01196-1", "arxiv": "2306.00572", "checked": "arXiv 2306.00572 and the JINA Virtual Journal listing of 2 June 2023, by web search (summarizes Wang et al. 2023, E_lab = 474.0 ± 1.1 keV, Jπ = 1⁻ and ωγ = 0.25 ± 0.03 µeV for the resonance that dominates the rate; the strength is not in the PRL abstract, so the site attributes it to this review); DOI from the Springer link in the same results; volume and article number not seen, 2026-10-13" }, "li2026": { "key": "li2026", "authors": "C. Li, H. Jia, Q. Wen, C. Lin et al.", "title": "S*(E) measurement of the ¹²C(¹²C,α)²⁰Ne reaction at astrophysical energies via the Trojan horse method with ¹⁶O quasi-free breakup", "journal": "Phys. Lett. B 879, 140675 (2026)", "year": 2026, "arxiv": "2609.08819", "checked": "arXiv 2609.08819 (journal reference given there), by web search (HI-13 tandem, CIAE; ¹⁶O as the Trojan horse nucleus; spectator α detected near 0°, described by the authors as a first in a THM experiment; S*(E) extracted with a DWBA-based analysis, as the authors describe it; resonances near 1.5 MeV in the α₀ and α₁ channels); DOI not seen, 2026-10-13" }, "li2026b": { "key": "li2026b", "authors": "C. Li, H. Jia et al.", "title": "Indirect measurement of the S*(E) factor for ¹²C(¹²C,p)²³Na at Gamow energies via the Trojan horse method with near-0 degree spectator detection", "journal": "arXiv preprint (2026)", "year": 2026, "arxiv": "2609.08837", "checked": "arXiv listing 2609.08837, submitted 8 September 2026, by web search (¹⁶O breakup at the HI-13 tandem; resonant structure near 1.5 MeV in the p₀ and p₁ channels and no hindrance in the measured range; trend qualitatively like Tumino et al. 2018, unlike the modified analysis of Mukhamedzhanov et al. 2019); no journal version seen, 2026-10-13" }, "mukhamedzhanov2026": { "key": "mukhamedzhanov2026", "authors": "A. M. Mukhamedzhanov", "title": "Breakdown of the plane-wave Trojan horse analysis of the ¹²C+¹²C fusion reaction: critical role of Coulomb distortions", "journal": "arXiv preprint (2026)", "year": 2026, "arxiv": "2609.04498", "checked": "arXiv 2609.04498 abstract, by web search (an analysis of the THM data of Li et al. 2026; Coulomb distortions change the energy dependence of the THM amplitude, matching the spectator momentum distribution does not validate the plane-wave approximation, so the plane-wave S-factor may not be reliable); no journal version seen, 2026-10-13" }, "ledererwoods2021": { "key": "ledererwoods2021", "authors": "C. Lederer-Woods et al. (n_TOF Collaboration)", "title": "Destruction of the cosmic γ-ray emitter ²⁶Al in massive stars: study of the key ²⁶Al(n,p) reaction", "journal": "Phys. Rev. C 104, L022803 (2021)", "year": 2021, "doi": "10.1103/PhysRevC.104.L022803", "checked": "KIT, INAF, Granada, Hertfordshire and IRB repository records, by web search (EAR2 at n_TOF; eleven resonance strengths, nine for the first time; significantly lower than the only previous values; data up to 150 keV, enough for rates up to 0.5 GK; open access, CC BY 4.0), 2026-10-13" }, "brandenburg2023": { "key": "brandenburg2023", "authors": "K. Brandenburg et al.", "title": "Measurements of the ¹³C(α,n)¹⁶O cross section up to E_α = 8 MeV", "journal": "Phys. Rev. C 108, L061601 (2023)", "year": 2023, "doi": "10.1103/PhysRevC.108.L061601", "checked": "APS abstract page, NSF PAR and JINA Virtual Journal records, by web search (published 20 December 2023; Edwards Accelerator Laboratory, Ohio University, ³He–BF₃ neutron barrel; E_α = 2.9–8.0 MeV; considerably lower than earlier direct data above 5 MeV, as Hauser–Feshbach corrections had suggested; thick-target yields above 6 MeV higher than those used for dark-matter and neutrino detector backgrounds), 2026-10-13" }, "balibreacorrea2026": { "key": "balibreacorrea2026", "authors": "J. Balibrea-Correa et al. (n_TOF Collaboration)", "title": "First ⁹⁴Nb(n,γ) measurement: constraining the nucleosynthetic origin of ⁹⁴Mo in presolar grains", "journal": "Phys. Rev. Lett. 137, 082701 (2026)", "year": 2026, "doi": "10.1103/538w-rhqb", "arxiv": "2603.17646", "checked": "APS abstract page, arXiv 2603.17646, the CERN and CERN EP newsletter news items and phys.org, by web search (published 18 August 2026; first measurement of the capture cross section of the radioactive branching point ⁹⁴Nb, where capture competes with β decay; presolar SiC grains show an excess of ⁹⁴Mo that models failed to reproduce; with the new Maxwellian-averaged cross section, fully coupled models of low-mass AGB stars agree with the grain data); CERN EP News calls the result an experimental validation of the general scale of earlier theoretical estimates (per the lit2 fact-check); no cross-section value is quoted on the site because none could be confirmed by search, 2026-10-13" }, "deboer2021": { "key": "deboer2021", "authors": "R. J. deBoer et al.", "title": "The ¹⁹F(p,γ)²⁰Ne and ¹⁹F(p,α)¹⁶O reaction rates and their effect on calcium production in Population III stars", "journal": "Phys. Rev. C 103, 055815 (2021)", "year": 2021, "checked": "Notre Dame ISNAP research highlight and JINA listing, and the APS DNP 2021 abstract that gives the journal reference, by web search (R-matrix fits of ¹⁹F(p,γ), (p,α) and (p,p) data together; the (p,γ) rate uncertainty is considerably larger than previously reported, because of unresolved interferences, a possible threshold state, possible subthreshold states, direct capture and higher resonances; more experiments needed); DOI not seen, 2026-10-13" }, "dong2024": { "key": "dong2024", "authors": "G. X. Dong, X. B. Wang, N. Michel, M. Płoszajczak", "title": "¹⁹F(p,γ)²⁰Ne reaction rate and the puzzling calcium abundance in metal poor stars", "journal": "arXiv preprint (2024)", "year": 2024, "arxiv": "2411.17243", "checked": "arXiv 2411.17243 abstract, November 2024, by web search (Gamow shell model in the coupled-channel representation; near 0.1 GK the predicted rate is close to the JUNA rate); no journal reference seen, 2026-10-13" }, "konopinski1946": { "key": "konopinski1946", "authors": "E. J. Konopinski, C. Marvin, E. Teller", "title": "Ignition of the atmosphere with nuclear bombs", "journal": "Los Alamos report LA-602 (1946)", "year": 1946, "checked": "Physics Today article of Wiescher and Langanke (2024) and the report's citations in the IF PAN seminar listing and Wikipedia, by web search (fusion of two ¹⁴N nuclei treated as the key reaction; radiation losses always exceed the nuclear energy gained under the report's assumptions, so no self-propagating burn is likely; the report still called further work highly desirable, per the NSF PAR copy of the Physics Today article); declassification year given as 1973 or 1979 by different sources, so not quoted, 2026-10-13" }, "wiescher2024pt": { "key": "wiescher2024pt", "authors": "M. Wiescher, K. Langanke", "title": "Manhattan Project astrophysics", "journal": "Phys. Today 77(3) (March 2024)", "year": 2024, "url": "https://physicstoday.aip.org/features/manhattan-project-astrophysics", "checked": "Physics Today feature page, the AAS notice of the March 2024 issue and the NSF PAR copy, by web search; page number and DOI not confirmed, so not given (Teller raised the fear of igniting the atmosphere at a 1942 meeting in Berkeley; Bethe estimated the probability as very low; the 1946 report of Teller, Konopinski and Marvin found no self-propagating chain likely; also ¹⁴N fusion with the hydrogen of water vapour; the wartime experience fed post-war nuclear astrophysics), 2026-10-13" }, "wiescher2024cool": { "key": "wiescher2024cool", "authors": "P. Wiescher, M. Wiescher", "title": "Cooling the atmosphere", "journal": "Natural Sciences 4, e20240005 (2024)", "year": 2024, "doi": "10.1002/ntls.20240005", "checked": "Wiley Online Library record (first published 22 April 2024), DOAJ record and Advanced Science News article, by web search (formerly classified 1940s experiments at the Notre Dame accelerator laboratory on radiation effects in materials and on how efficiently the atmosphere cools the fireball of a fission device), 2026-10-13" }, "wiescher2025": { "key": "wiescher2025", "authors": "M. Wiescher, K. Langanke", "title": "The astrophysical thoughts of Carl Friedrich von Weizsäcker", "journal": "Phys. Perspect. 27, 26 (2025)", "year": 2025, "doi": "10.1007/s00016-025-00325-0", "checked": "Springer article page and GSI repository record, by web search (pp. 26–49, CC BY 4.0; from Weizsäcker's notes and letters, 1935–1945; after his papers of 1937 and 1938 he turned to fission and the war, but kept thinking about neutron stars and cosmology; the CN cycle was tied for him to a change in the paradigm for the origin of the elements), 2026-10-13" }, "kaeppeler2011": { "key": "kaeppeler2011", "authors": "F. Käppeler, R. Gallino, S. Bisterzo, W. Aoki", "title": "The s process: nuclear physics, stellar models, and observations", "journal": "Rev. Mod. Phys. 83, 157 (2011)", "year": 2011, "doi": "10.1103/RevModPhys.83.157", "arxiv": "1012.5218", "checked": "arXiv 1012.5218 listing (authors, abstract) and a 2025 arXiv paper citing the published version with its DOI, 2026-10-12" }, "clayton1961": { "key": "clayton1961", "authors": "D. D. Clayton, W. A. Fowler, T. E. Hull, B. A. Zimmerman", "title": "Neutron capture chains in heavy element synthesis", "journal": "Ann. Phys. 12, 331 (1961)", "year": 1961, "doi": "10.1016/0003-4916(61)90067-7", "checked": "biography page listing volume, page, ADS bibcode 1961AnPhy..12..331C and DOI; D. D. Clayton's 1962 Caltech thesis (Part I is a reprint of this article), 2026-10-12" }, "bao2000": { "key": "bao2000", "authors": "Z. Y. Bao, H. Beer, F. Käppeler, F. Voss, K. Wisshak, T. Rauscher", "title": "Neutron cross sections for nucleosynthesis studies", "journal": "At. Data Nucl. Data Tables 76, 70 (2000)", "year": 2000, "doi": "10.1006/adnd.2000.0838", "checked": "University of Hertfordshire and Basel repository records (pp. 70–154, DOI, abstract giving recommended MACS at kT = 30 keV for H to Bi), 2026-10-12" }, "dillmann2008": { "key": "dillmann2008", "authors": "I. Dillmann et al.", "title": "New stellar (n,γ) cross sections and the \"Karlsruhe Astrophysical Database of Nucleosynthesis in Stars\"", "journal": "Proc. Int. Conf. on Nuclear Data for Science and Technology 2007 (EDP Sciences, 2008), p. 575", "year": 2008, "doi": "10.1051/ndata:07303", "arxiv": "0806.2076", "checked": "arXiv 0806.2076 listing and University of Hertfordshire repository record (pages 575–578, DOI), 2026-10-12" }, "straniero2006": { "key": "straniero2006", "authors": "O. Straniero, R. Gallino, S. Cristallo", "title": "s process in low-mass asymptotic giant branch stars", "journal": "Nucl. Phys. A 777, 311 (2006)", "year": 2006, "doi": "10.1016/j.nuclphysa.2005.01.011", "arxiv": "astro-ph/0501405", "checked": "arXiv astro-ph/0501405 (abstract; ¹³C pocket burning radiatively at kT ≈ 8 keV, ²²Ne(α,n) in the pulses, ¹⁴N(n,p) as poison) and JINA Virtual Journal listing (Nucl. Phys. A 777); pages 311–339 and DOI from the arXiv journal reference, by web search, 2026-10-12" }, "dillmann2014": { "key": "dillmann2014", "authors": "I. Dillmann, T. Szücs, R. Plag, Z. Fülöp, F. Käppeler, A. Mengoni, T. Rauscher", "title": "The Karlsruhe Astrophysical Database of Nucleosynthesis in Stars project – status and prospects", "journal": "Nucl. Data Sheets 120, 171 (2014)", "year": 2014, "arxiv": "1408.3688", "checked": "arXiv 1408.3688 and University of Basel repository record (pp. 171–174, authors); KADoNiS v1.0 project page, by web search, 2026-10-12" }, "carlson2018": { "key": "carlson2018", "authors": "A. D. Carlson et al.", "title": "Evaluation of the neutron data standards", "journal": "Nucl. Data Sheets 148, 143 (2018)", "year": 2018, "doi": "10.1016/j.nds.2018.02.002", "checked": "ANU and OSTI repository records (pp. 143–188, DOI; the Maxwellian-averaged ¹⁹⁷Au(n,γ) cross section at 30 keV evaluated as a non-traditional standard) and the IAEA standards table (620 ± 11 mb), by web search, 2026-10-12" }, "lugaro2011": { "key": "lugaro2011", "authors": "M. Lugaro, A. Chieffi", "title": "Radioactivities in low- and intermediate-mass stars", "journal": "Lect. Notes Phys. 812, 83 (2011)", "year": 2011, "arxiv": "1010.1304", "checked": "arXiv 1010.1304 (about 40% of ⁸⁴Kr(n,γ) captures feed the 4.5 h isomer of ⁸⁵Kr, about 80% of which decays to ⁸⁵Rb; ⁸⁵Kr ground state 10.7 yr); volume and page from the Astronomy with Radioactivities book, by web search, 2026-10-12" }, "wallner2016": { "key": "wallner2016", "authors": "A. Wallner et al.", "title": "Accelerator mass spectrometry measurements of the ¹³C(n,γ)¹⁴C and ¹⁴N(n,p)¹⁴C cross sections", "journal": "Phys. Rev. C 93, 045803 (2016)", "year": 2016, "doi": "10.1103/PhysRevC.93.045803", "checked": "University of Vienna and ANU repository records (journal, 11 April 2016, abstract); DOI by APS scheme, 2026-10-12" }, "torressanchez2023": { "key": "torressanchez2023", "authors": "P. Torres-Sánchez et al. (n_TOF Collaboration)", "title": "Measurement of the ¹⁴N(n,p)¹⁴C cross section at the CERN n_TOF facility from subthermal energy to 800 keV", "journal": "Phys. Rev. C 107, 064617 (2023)", "year": 2023, "doi": "10.1103/PhysRevC.107.064617", "arxiv": "2212.05128", "checked": "University of Granada repository record (first author, arXiv 2212.05128), KIT and Vienna records (abstract); DOI by APS scheme, 2026-10-12" }, "beer2002": { "key": "beer2002", "authors": "H. Beer, P. V. Sedyshev, W. Rochow, P. Mohr, H. Oberhummer", "title": "Neutron capture measurements of the noble gas isotopes ²²Ne, ⁴⁰Ar and ⁷⁸,⁸⁰,⁸⁴,⁸⁶Kr in the keV energy region", "journal": "Nucl. Phys. A 705, 239 (2002)", "year": 2002, "checked": "TU Darmstadt and University of Basel repository records (authors, title, volume) and an EXFOR entry citing Nucl. Phys. A 705, 239 with Maxwellian-averaged cross sections of ²²Ne, by web search, 2026-10-12" }, "tomyo2003": { "key": "tomyo2003", "authors": "A. Tomyo, Y. Nagai, Y. Nobuhara, T. Shima, H. Makii, K. Mishima, M. Igashira", "title": "Neutron capture cross section measurement of ²⁰,²²Ne for stellar nucleosynthesis", "journal": "Nucl. Phys. A 718, 527c (2003)", "year": 2003, "checked": "EXFOR entry 22775 (authors, Tokyo Institute of Technology; main reference Nucl. Phys. A 718, 527c (2003), a conference contribution) and ETDE/OSTI record (title, journal), by web search, 2026-10-12. The group's time-of-flight letter, cited in reviews as ApJ 623, L153 (2005), could not be confirmed from any record (two searches, 2026-10-12), so it is not cited." }, "massimi2012": { "key": "massimi2012", "authors": "C. Massimi et al. (n_TOF Collaboration)", "title": "Resonance neutron-capture cross sections of stable magnesium isotopes and their astrophysical implications", "journal": "Phys. Rev. C 85, 044615 (2012)", "year": 2012, "doi": "10.1103/PhysRevC.85.044615", "checked": "University of Seville and Hertfordshire repository records (n_TOF capture data with a shape analysis together with transmission data; MACS at 30 keV 3.8 ± 0.2, 4.1 ± 0.6 and 0.14 ± 0.01 mb for ²⁴,²⁵,²⁶Mg; ²⁵Mg the most important poison in massive stars of solar metallicity); DOI by APS scheme, by web search, 2026-10-12" }, "heil2014": { "key": "heil2014", "authors": "M. Heil et al.", "title": "Stellar neutron capture cross sections of ²⁰,²¹,²²Ne", "journal": "Phys. Rev. C 90, 045804 (2014)", "year": 2014, "doi": "10.1103/PhysRevC.90.045804", "checked": "University of Hull repository record (pp. 045804-1–11, DOI, abstract: SAMMY R-matrix reanalysis of keV resonance data) and the IAEA PGAA ²²Ne(n,γ) report; an erratum appeared as Phys. Rev. C 92, 019902 (2015), 2026-10-12" }, "igashira1995": { "key": "igashira1995", "authors": "M. Igashira, Y. Nagai, K. Masuda, T. Ohsaki, H. Kitazawa", "title": "Measurement of the ¹⁶O(n,γ)¹⁷O reaction cross section at stellar energy and the critical role of nonresonant p-wave neutron capture", "journal": "Astrophys. J. 441, L89 (1995)", "year": 1995, "checked": "EXFOR entry 22356, IAEA PGAA report and ENSDF summary (10–80 keV, MACS, nonresonant p-wave capture); DOI not confirmed, 2026-10-12" }, "mohr2016": { "key": "mohr2016", "authors": "P. Mohr, C. Heinz, M. Pignatari, I. Dillmann, A. Mengoni, F. Käppeler", "title": "Re-evaluation of the ¹⁶O(n,γ)¹⁷O cross section at astrophysical energies and its role as neutron poison in the s process", "journal": "Astrophys. J. 827, 29 (2016)", "year": 2016, "arxiv": "1605.02639", "checked": "arXiv 1605.02639 listing (abstract; kT = 26 keV in core helium burning and 90 keV in shell carbon burning) and University of Hull repository record (ApJ 827, issue 1); article number not shown by the records found, DOI omitted, 2026-10-12" }, "wang2014": { "key": "wang2014", "authors": "T.-F. Wang et al.", "title": "Maxwellian averaged neutron capture cross sections in ⁵⁶Fe and ⁵⁷Fe", "journal": "Chin. Phys. Lett. 31, 092101 (2014)", "year": 2014, "doi": "10.1088/0256-307X/31/9/092101", "checked": "Chinese Physics Letters abstract page (⁷Li(p,n) source, time of flight, MACS of ⁵⁶Fe and ⁵⁷Fe) and Beihang University record, 2026-10-12" }, "lederer2013": { "key": "lederer2013", "authors": "C. Lederer et al. (n_TOF Collaboration)", "title": "Neutron capture cross section of unstable ⁶³Ni: implications for stellar nucleosynthesis", "journal": "Phys. Rev. Lett. 110, 022501 (2013)", "year": 2013, "doi": "10.1103/PhysRevLett.110.022501", "arxiv": "1304.3310", "checked": "arXiv 1304.3310 abstract (first measurement, thermal to 200 keV, 12 resonances, MACS kT = 5–100 keV with ≈ 20% uncertainty; previous KADoNiS 30 keV value 31 ± 6 mb) and Hertfordshire, UPC and Seville repository records with the DOI, 2026-10-12" }, "lederer2014": { "key": "lederer2014", "authors": "C. Lederer et al. (n_TOF Collaboration)", "title": "⁶²Ni(n,γ) and ⁶³Ni(n,γ) cross sections measured at the n_TOF facility at CERN", "journal": "Phys. Rev. C 89, 025810 (2014)", "year": 2014, "doi": "10.1103/PhysRevC.89.025810", "arxiv": "1403.4778", "checked": "arXiv 1403.4778 and Seville, JRC and ANU repository records (42 ⁶²Ni resonances, MACS 4.5% uncertainty, agreement with KADoNiS at 30 keV, up to a factor 1.6 lower at higher kT; ⁶³Ni 10–270 keV, 17% systematic); DOI by APS scheme, 2026-10-12" }, "weigand2015": { "key": "weigand2015", "authors": "M. Weigand et al.", "title": "⁶³Ni(n,γ) cross sections measured with DANCE", "journal": "Phys. Rev. C 92, 045810 (2015)", "year": 2015, "doi": "10.1103/PhysRevC.92.045810", "arxiv": "1512.02263", "checked": "arXiv 1512.02263 and ANU and Frankfurt repository records (DANCE at LANSCE, relative to ¹⁹⁷Au, uncertainties below 15%), 2026-10-12" }, "raut2013": { "key": "raut2013", "authors": "R. Raut, A. P. Tonchev, G. Rusev, W. Tornow, C. Iliadis, M. Lugaro, J. Buntain, S. Goriely, J. H. Kelley, R. Schwengner, A. Banu, N. Tsoneva", "title": "Cross-section measurements of the ⁸⁶Kr(γ,n) reaction to probe the s-process branching at ⁸⁵Kr", "journal": "Phys. Rev. Lett. 111, 112501 (2013)", "year": 2013, "doi": "10.1103/PhysRevLett.111.112501", "arxiv": "1309.4159", "checked": "Duke Scholars and HZDR records (journal, DOI, HIγS photon beams from 9.86 to 13 MeV, abstract), arXiv 1309.4159, 2026-10-12" }, "abbondanno2004": { "key": "abbondanno2004", "authors": "U. Abbondanno et al. (n_TOF Collaboration)", "title": "Neutron capture cross section measurement of ¹⁵¹Sm at the CERN neutron time of flight facility (n_TOF)", "journal": "Phys. Rev. Lett. 93, 161103 (2004)", "year": 2004, "doi": "10.1103/PhysRevLett.93.161103", "checked": "HAL in2p3-00026025 and University of Hertfordshire records (1 eV–1 MeV; MACS at kT = 30 keV of 3100 ± 160 mb); DOI by APS scheme, 2026-10-12" }, "wisshak2006": { "key": "wisshak2006", "authors": "K. Wisshak, F. Voss, F. Käppeler, M. Krtička, S. Raman, A. Mengoni, R. Gallino", "title": "Stellar neutron capture cross section of the unstable s-process branching point ¹⁵¹Sm", "journal": "Phys. Rev. C 73, 015802 (2006)", "year": 2006, "doi": "10.1103/PhysRevC.73.015802", "checked": "EXFOR entry 22916 (authors, reference, 3.7 MV Van de Graaff and the Karlsruhe 4π BaF₂ detector) and a catalogue record giving the title; DOI by APS scheme, 2026-10-12" }, "heil2008lu": { "key": "heil2008lu", "authors": "M. Heil, N. Winckler, S. Dababneh, F. Käppeler, K. Wisshak, S. Bisterzo, R. Gallino, A. M. Davis, T. Rauscher", "title": "¹⁷⁶Lu/¹⁷⁶Hf: a sensitive test of s-process temperature and neutron density in AGB stars", "journal": "Astrophys. J. 673, 434 (2008)", "year": 2008, "checked": "University of Hertfordshire and Basel repository records (pp. 434–444, abstract: partial cross section to the ¹⁷⁶Lu isomer by activation at Karlsruhe, temperature-dependent β half-life), 2026-10-12" }, "beer1980": { "key": "beer1980", "authors": "H. Beer, F. Käppeler", "title": "Neutron capture cross sections on ¹³⁸Ba, ¹⁴⁰,¹⁴²Ce, ¹⁷⁵,¹⁷⁶Lu, and ¹⁸¹Ta at 30 keV; prerequisite for investigation of the ¹⁷⁶Lu cosmic clock", "journal": "Phys. Rev. C 21, 534 (1980)", "year": 1980, "doi": "10.1103/PhysRevC.21.534", "checked": "DOI resolver listing and EXFOR entry 21647 (activation at a pulsed Van de Graaff, 1.911 MeV protons on ⁷Li giving a nearly Maxwellian spectrum of 22–24 keV, partial cross section to the 3.68 h isomer of ¹⁷⁶Lu), 2026-10-12" }, "takahashi1987": { "key": "takahashi1987", "authors": "K. Takahashi, K. Yokoi", "title": "Beta-decay rates of highly ionized heavy atoms in stellar interiors", "journal": "At. Data Nucl. Data Tables 36, 375 (1987)", "year": 1987, "doi": "10.1016/0092-640X(87)90010-6", "checked": "ADS record 1987ADNDT..36..375T (title, authors, volume 36, pp. 375–409) and the reference lists of Eur. Phys. J. A 59 (2023) and A&A 538 (2012) giving the same volume, page and DOI, by web search, 2026-10-12" }, "ratynski1988": { "key": "ratynski1988", "authors": "W. Ratynski, F. Käppeler", "title": "Neutron capture cross section of ¹⁹⁷Au: a standard for stellar nucleosynthesis", "journal": "Phys. Rev. C 37, 595 (1988)", "year": 1988, "doi": "10.1103/PhysRevC.37.595", "checked": "INSPIRE record 275787 (pp. 595–604, abstract: 648 ± 10 mb at kT = 25 keV, 582 ± 9 mb extrapolated to 30 keV) and EXFOR entry 22099 (protons at 1912 keV); DOI by APS scheme, 2026-10-12" }, "lederer2011": { "key": "lederer2011", "authors": "C. Lederer et al. (n_TOF Collaboration)", "title": "¹⁹⁷Au(n,γ) cross section in the unresolved resonance region", "journal": "Phys. Rev. C 83, 034608 (2011)", "year": 2011, "doi": "10.1103/PhysRevC.83.034608", "checked": "University of Vienna, Seville, UPC and Hertfordshire repository records (5–400 keV, C₆D₆ detectors, 3.9–6.7% uncertainty, MACS at 30 keV 4.7% above the activation value), 2026-10-12" }, "massimi2014": { "key": "massimi2014", "authors": "C. Massimi, B. Becker, E. Dupont, S. Kopecky, C. Lampoudis, R. Massarczyk, M. Moxon, V. Pronyaev, P. Schillebeeckx, I. Sirakov, R. Wynants", "title": "Neutron capture cross section measurements for ¹⁹⁷Au from 3.5 to 84 keV at GELINA", "journal": "Eur. Phys. J. A 50, 124 (2014)", "year": 2014, "doi": "10.1140/epja/i2014-14124-8", "checked": "Springer article page and University of Bologna and JRC repository records (C₆D₆ detectors at about 13 m, normalised to the 4.9 eV resonance; results more than 5% from the astrophysical reference value), 2026-10-12" }, "domingopardo2006": { "key": "domingopardo2006", "authors": "C. Domingo-Pardo et al. (n_TOF Collaboration)", "title": "New measurement of neutron capture resonances in ²⁰⁹Bi", "journal": "Phys. Rev. C 74, 025807 (2006)", "year": 2006, "doi": "10.1103/PhysRevC.74.025807", "arxiv": "nucl-ex/0610040", "checked": "arXiv nucl-ex/0610040 and HAL in2p3-00098239 and Hertfordshire records (pulse-height weighting at n_TOF; rate at kT = 5–8 keV about 16% above the accepted value; s fraction of solar Bi 19 ± 3%); DOI by APS scheme, 2026-10-12. Introduction re-checked on 2026-10-12 — branchings in the α recycling at ²¹⁰Po (138 d) and at ²¹⁰Biᵐ (3 Myr); ²¹⁰Po may capture a neutron and enhance ²⁰⁷Pb; capture on the 271 keV isomer of ²¹⁰Bi leads to ²¹¹Bi (α, 2.17 min), another contribution to ²⁰⁷Pb" }, "ratzel2004": { "key": "ratzel2004", "authors": "U. Ratzel, C. Arlandini, F. Käppeler et al.", "title": "Nucleosynthesis at the termination point of the s process", "journal": "Phys. Rev. C 70, 065803 (2004)", "year": 2004, "doi": "10.1103/PhysRevC.70.065803", "checked": "ResearchGate and library records (December 2004, DOI; abstract on stellar cross sections of ²⁰⁸Pb(n,γ) and ²⁰⁹Bi(n,γ)²¹⁰Bi, capture to the ²¹⁰Bi ground state that decays to ²¹⁰Po, recycling at the termination point in a 3 M☉, [Fe/H] = −1.3 AGB model), by web search, 2026-10-12. Re-checked on 2026-10-12 (round 4) — no record available to us confirms that the ²¹⁰Bi isomer is depopulated to the ground state in the star, so the site no longer cites this paper for that statement" }, "jung1992": { "key": "jung1992", "authors": "M. Jung, F. Bosch et al.", "title": "First observation of bound-state β⁻ decay", "journal": "Phys. Rev. Lett. 69, 2164 (1992)", "year": 1992, "doi": "10.1103/PhysRevLett.69.2164", "checked": "reviews arXiv nucl-th/9611029 and 2003.05201 (bare ¹⁶³Dy⁶⁶⁺ in the GSI ESR, t½ = 47 +5/−4 d, Q of the bound-state channel 50.3 keV) and an archive record of the title and authors; volume and page as cited in the literature, DOI by APS scheme, by web search, 2026-10-12" }, "reifarth2009": { "key": "reifarth2009", "authors": "R. Reifarth et al.", "title": "Opportunities for nuclear astrophysics at FRANZ", "journal": "Publ. Astron. Soc. Aust. 26, 255 (2009)", "year": 2009, "doi": "10.1071/AS08061", "arxiv": "0909.5279", "checked": "arXiv 0909.5279 and the CSIRO journal record (pp. 255–258, DOI), 2026-10-12" }, "tessler2015": { "key": "tessler2015", "authors": "M. Tessler, M. Paul et al.", "title": "Stellar 30-keV neutron capture in ⁹⁴,⁹⁶Zr and the ⁹⁰Zr(γ,n)⁸⁹Zr photonuclear reaction with a high-power liquid-lithium target", "journal": "Phys. Lett. B 751, 418 (2015)", "year": 2015, "arxiv": "1511.04701", "checked": "arXiv 1511.04701 and DOAJ journal record (pp. 418–422; LiLiT at SARAF, quasi-Maxwellian kT ≈ 30 keV, 3–5 × 10¹⁰ n/s; MACS 28.0 ± 0.6 mb for ⁹⁴Zr and 12.4 ± 0.5 mb for ⁹⁶Zr), 2026-10-12" }, "merrill1952": { "key": "merrill1952", "authors": "P. W. Merrill", "title": "Spectroscopic observations of stars of class S", "journal": "Astrophys. J. 116, 21 (1952)", "year": 1952, "doi": "10.1086/145589", "checked": "Wikipedia articles on technetium stars and on P. W. Merrill (citation with bibcode 1952ApJ...116...21M and DOI) and FRIB/MSU history articles (technetium lines in R Andromedae and other S-type red giants, 1952), by web search, 2026-10-12" }, "bernatowicz1987": { "key": "bernatowicz1987", "authors": "T. Bernatowicz, G. Fraundorf, T. Ming, E. Anders, B. Wopenka, E. Zinner, P. Fraundorf", "title": "Evidence for interstellar SiC in the Murray carbonaceous meteorite", "journal": "Nature 330, 728 (1987)", "year": 1987, "doi": "10.1038/330728a0", "checked": "Nature article page and NASA NTRS and UMSL records (SiC grains of 0.1–1 μm in Murray separates rich in anomalous Ne and Xe; C, N and Si isotopes point to a presolar origin, probably in red-giant atmospheres), by web search, 2026-10-12" }, "vaneck2001": { "key": "vaneck2001", "authors": "S. Van Eck, S. Goriely, A. Jorissen, B. Plez", "title": "Discovery of three lead-rich stars", "journal": "Nature 412, 793 (2001)", "year": 2001, "doi": "10.1038/35090514", "checked": "Nature abstract, IDEAS/RePEc and Montpellier records (HD 187861, HD 196944, HD 224959: low-metallicity stars more enriched in lead than in any other element beyond iron, as predicted for AGB stars of low metallicity), by web search, 2026-10-12" }, "cowan1977": { "key": "cowan1977", "authors": "J. J. Cowan, W. K. Rose", "title": "Production of ¹⁴C and neutrons in red giants", "journal": "Astrophys. J. 212, 149 (1977)", "year": 1977, "doi": "10.1086/155030", "checked": "DOI record and ADS bibcode 1977ApJ...212..149C (hydrogen mixed into the helium-flash convective zone; neutron flux many orders of magnitude above the classical s-process, suggesting an intermediate process), by web search, 2026-10-12" }, "hampel2016": { "key": "hampel2016", "authors": "M. Hampel, R. J. Stancliffe, M. Lugaro, B. S. Meyer", "title": "The intermediate neutron-capture process and carbon-enhanced metal-poor stars", "journal": "Astrophys. J. 831, 171 (2016)", "year": 2016, "doi": "10.3847/0004-637X/831/2/171", "arxiv": "1608.08634", "checked": "Heidelberg library record and arXiv 1608.08634 listing (network calculations at constant neutron densities of 10⁷–10¹⁵ cm⁻³; the i process between the s and r densities as an explanation of CEMP-s/r stars), by web search, 2026-10-12" }, "reifarth2003": { "key": "reifarth2003", "authors": "R. Reifarth et al.", "title": "Stellar neutron capture on promethium: implications for the s-process neutron density", "journal": "Astrophys. J. 582, 1251 (2003)", "year": 2003, "checked": "University of Hertfordshire record and EXFOR entry 22829 (activation at Karlsruhe of a 28 ng ¹⁴⁷Pm sample, about 10¹⁴ atoms; partial cross sections to the ground state and the 41.3 d isomer of ¹⁴⁸Pm; total 709 ± 100 mb at kT = 30 keV), by web search, 2026-10-12" }, "guerrero2020": { "key": "guerrero2020", "authors": "C. Guerrero et al. (n_TOF Collaboration)", "title": "Neutron capture on the s-process branching point ¹⁷¹Tm via time-of-flight and activation", "journal": "Phys. Rev. Lett. 125, 142701 (2020)", "year": 2020, "doi": "10.1103/PhysRevLett.125.142701", "checked": "INAF, KIT, ANU and JRC repository records (first resonance parameters of ¹⁷¹Tm at n_TOF; activation at SARAF-LiLiT giving a MACS at 30 keV of 384(40) mb, 2.6 times below JEFF-3.3 and ENDF/B-VIII; sample made at ILL and PSI); DOI by APS scheme, by web search, 2026-10-12" }, "casanovashoste2024": { "key": "casanovashoste2024", "authors": "A. Casanovas-Hoste et al. (n_TOF Collaboration)", "title": "Shedding light on the origin of ²⁰⁴Pb, the heaviest s-process-only isotope in the Solar System", "journal": "Phys. Rev. Lett. 133, 052702 (2024)", "year": 2024, "doi": "10.1103/PhysRevLett.133.052702", "checked": "KIT, ANU, Granada and CIEMAT repository records (first measurement of ²⁰⁴Tl(n,γ), at n_TOF with 9 mg of ²⁰⁴Tl made at the ILL; MACS 580(168) mb at kT ≈ 8 keV and 260(90) mb at 30 keV), by web search, 2026-10-12" }, "tagliente2013": { "key": "tagliente2013", "authors": "G. Tagliente et al. (n_TOF Collaboration)", "title": "The ⁹³Zr(n,γ) reaction up to 8 keV neutron energy", "journal": "Phys. Rev. C 87, 014622 (2013)", "year": 2013, "doi": "10.1103/PhysRevC.87.014622", "checked": "Seville, Bologna, HAL in2p3-00824209 and JRC records (resonance parameters of the radioactive ⁹³Zr at n_TOF up to 8 keV; capture widths about 14% smaller than in an earlier experiment); DOI by APS scheme, by web search, 2026-10-12" }, "weiss2015": { "key": "weiss2015", "authors": "C. Weiss et al.", "title": "The new vertical neutron beam line at the CERN n_TOF facility design and outlook on the performance", "journal": "Nucl. Instrum. Methods A 799, 90 (2015)", "year": 2015, "checked": "HAL in2p3-01266473, Vienna, Granada and Hertfordshire records (the vertical beam line EAR2, built in 2014, FLUKA design for a higher flux), with the flight paths of 185 m (EAR1) and about 20 m (EAR2) from n_TOF NEAR-station papers, by web search, 2026-10-12" }, "patronis2023": { "key": "patronis2023", "authors": "N. Patronis, A. Mengoni, S. Goula et al. (n_TOF Collaboration)", "title": "Status report of the n_TOF facility after the 2nd CERN long shutdown period", "journal": "EPJ Tech. Instrum. 10, 13 (2023)", "year": 2023, "doi": "10.1140/epjti/s40485-023-00100-w", "checked": "SpringerOpen article page and Granada, HZDR and Edinburgh records (new nitrogen-cooled lead spallation target in 2019–2021; the NEAR station close to the target for activation measurements), by web search, 2026-10-12" }, "schanz1991": { "key": "schanz1991", "authors": "W. Schanz, G. Rupp, F. Käppeler", "title": "The stellar cross sections of ¹²⁰Sn, ¹²¹Sb, ¹²³Sb and ¹²⁸Te – a study of possible s-process branchings at A = 121, 122", "journal": "Report KfK-4953 (NEANDC(E)-322 U Vol. 5), Kernforschungszentrum Karlsruhe (1991)", "year": 1991, "url": "https://publikationen.bibliothek.kit.edu/270031359", "checked": "KIT library catalogue record (title, authors, 1991, in the German nuclear-data progress report KfK-4953), by web search, 2026-10-12" } }, "facilities": [ { "id": "luna-50", "name": "LUNA 50 kV", "lab": "Laboratori Nazionali del Gran Sasso (INFN)", "location": "Assergi, L'Aquila", "country": "Italy", "underground": true, "depth": "about 1400 m of rock, 3800 metres water equivalent", "accelerator": "50 kV ion accelerator with a windowless gas target", "years": "described in 1994; first results on ³He(³He,2p)⁴He in 1996", "luna": true, "summary": "The first accelerator built deep underground for nuclear astrophysics. It was a small pilot machine, installed under the Gran Sasso mountain to show that the rock overhead removes enough cosmic-ray background to measure fusion reactions at the energies found in the Sun.", "details": "Compact 50 kV accelerator with a windowless, differentially pumped gas target, a beam calorimeter for the current measurement and silicon detector telescopes for the charged reaction products. It was designed for ³He(³He,2p)⁴He in the solar Gamow peak, which it reached down to 16.5 keV.", "refs": [ "greife1994", "arpesella1996", "junker1998", "bonetti1999", "broggini2010" ] }, { "id": "luna-400", "name": "LUNA 400 kV", "lab": "Laboratori Nazionali del Gran Sasso (INFN)", "location": "Assergi, L'Aquila", "country": "Italy", "underground": true, "depth": "about 1400 m of rock, 3800 metres water equivalent", "accelerator": "400 kV electrostatic accelerator (LUNA II)", "years": "in operation from the early 2000s (facility paper 2003)", "luna": true, "summary": "The second LUNA accelerator, installed at Gran Sasso after the 50 kV pilot machine. Its very stable proton beam has been used for most of the underground measurements of hydrogen burning.", "details": "High-current 400 kV accelerator. Resonance scans gave an absolute proton energy known to about ±300 eV, an energy spread below 100 eV and a long-term drift of about 5 eV per hour. It has served both solid targets with HPGe detectors and a windowless gas target with a 4π BGO summing detector.", "refs": [ "formicola2003", "broggini2010", "lemut2006" ] }, { "id": "bellotti-ibf", "name": "Bellotti Ion Beam Facility (BIBF)", "lab": "Laboratori Nazionali del Gran Sasso (INFN)", "location": "Assergi, L'Aquila", "country": "Italy", "underground": true, "depth": "about 1400 m of rock, 3800 metres water equivalent", "accelerator": "3.5 MV Singletron (High Voltage Engineering Europa), terminal voltage 0.3–3.5 MV, ECR ion source", "years": "installed 2022; inaugurated October 2023", "luna": true, "url": "https://www.chetec-infra.eu/ta/tna-labs/bellotti-ion-beam-facility/", "summary": "An underground accelerator laboratory at Gran Sasso with a 3.5 MV machine, named after Enrico Bellotti, the first director of the laboratory. Its proton, helium and carbon beams extend underground measurements from hydrogen burning to helium and carbon burning.", "details": "The Singletron has a 10 GHz permanent-magnet ECR source and delivers about 1 mA of protons, 0.5 mA of helium and 0.15 mA of carbon. The design paper reports an energy stability better than 10⁻⁵ and a terminal-voltage ripple of 1.5 × 10⁻⁵. The facility is run as a user facility by the LNGS accelerator service, with beam time allocated through yearly calls.", "refs": [ "sen2019", "junker2023" ] }, { "id": "juna", "name": "JUNA", "lab": "China Jinping Underground Laboratory", "location": "Jinping, Sichuan", "country": "China", "underground": true, "depth": "about 2400 m of marble, 6720 metres water equivalent", "accelerator": "400 kV high-current platform with ECR ion sources (H⁺, He⁺, He²⁺)", "years": "first experiments underground in early 2021", "summary": "The Jinping Underground laboratory for Nuclear Astrophysics, a high-current accelerator deep inside a mountain in south-west China. Like LUNA, it uses the rock above it to reduce the background from cosmic rays.", "details": "The 400 kV platform was designed for 10 emA of H⁺ and He⁺ and 2 emA of He²⁺ from ECR sources. It ran for more than 2000 hours underground in early 2021, with BGO and neutron detectors, on reactions including ¹²C(α,γ)¹⁶O, ¹³C(α,n)¹⁶O, ²⁵Mg(p,γ)²⁶Al and ¹⁹F(p,α)¹⁶O. The muon flux measured at the laboratory is (3.53 ± 0.22 ± 0.07) × 10⁻¹⁰ cm⁻² s⁻¹.", "refs": [ "zhang2022" ] }, { "id": "caspar", "name": "CASPAR", "lab": "Sanford Underground Research Facility", "location": "Lead, South Dakota", "country": "United States", "underground": true, "depth": "4850 ft level, 4300 metres water equivalent", "accelerator": "JN Van de Graaff, about 150 kV to 1.1 MV, moved from Notre Dame", "years": "first beam 2017, inaugurated July 2017", "url": "https://sanfordlab.org/experiments/caspar", "summary": "The Compact Accelerator System for Performing Astrophysical Research, an underground accelerator in the former Homestake gold mine, where Davis ran his solar neutrino experiment. It is used mainly for helium-induced reactions, including the stellar neutron sources.", "details": "A JN-type Van de Graaff that ran above ground at Notre Dame was moved to the 4850 ft level of SURF from 2015. It delivers proton and α beams of 200–250 μA on target. The CASPAR collaboration gives a muon flux of about 4.4 × 10⁻⁹ cm⁻² s⁻¹. CASPAR is run by Notre Dame, the South Dakota School of Mines and Technology and the Colorado School of Mines." }, { "id": "felsenkeller", "name": "Felsenkeller 5 MV", "lab": "Felsenkeller underground laboratory (HZDR and TU Dresden)", "location": "Dresden", "country": "Germany", "underground": true, "depth": "45 m of rock", "accelerator": "5 MV Pelletron (NEC 15SDH-2), with an external sputter ion source and an internal RF source", "years": "inaugurated 4 July 2019", "url": "https://hzdr.de/db/Cms?pNid=1029", "summary": "A shallow-underground accelerator laboratory in tunnels under a hill in Dresden. The rock above it, together with detectors that veto cosmic-ray muons, lowers the background enough for many reactions that are hard to measure at the surface.", "details": "The rock reduces the muon flux by a factor of 40 and the neutron flux by a factor of 180 with respect to the surface. With an active muon veto the γ-ray background is about twice that of a deep underground site. The Pelletron was used before for ¹⁴C accelerator mass spectrometry in York. Typical beam currents are up to 30 μA for helium and carbon. The laboratory is run jointly by HZDR and TU Dresden." }, { "id": "hzdr", "name": "HZDR Tandetron, Dresden-Rossendorf", "lab": "Helmholtz-Zentrum Dresden-Rossendorf", "location": "Dresden", "country": "Germany", "underground": false, "accelerator": "3 MV Tandetron of the HZDR Ion Beam Center", "summary": "A surface tandem accelerator at the Helmholtz centre in Dresden, used for proton- and alpha-capture measurements." }, { "id": "bochum", "name": "Dynamitron Tandem Laboratory, Bochum", "lab": "Ruhr-Universität Bochum", "location": "Bochum", "country": "Germany", "underground": false, "accelerator": "4 MV Dynamitron tandem", "summary": "A university accelerator laboratory with a long record in low-energy nuclear astrophysics at the surface." }, { "id": "notre-dame", "name": "Nuclear Science Laboratory, Notre Dame", "lab": "University of Notre Dame", "location": "Notre Dame, Indiana", "country": "United States", "underground": false, "accelerator": "10 MV FN tandem, 5 MV Sta. Ana single-ended Pelletron (2012), 3 MV St. Andre tandem (2017)", "url": "https://isnap.nd.edu/research/facility/accelerator/", "summary": "A university laboratory with several accelerators for nuclear astrophysics, used for capture and alpha-induced reactions. The St. George recoil separator is part of it." }, { "id": "st-george", "name": "St. George recoil separator", "lab": "University of Notre Dame", "location": "Notre Dame, Indiana", "country": "United States", "underground": false, "accelerator": "recoil separator on the 5 MV Sta. Ana accelerator", "summary": "A recoil separator built to study helium captures in inverse kinematics. A heavy beam hits a helium gas target, and the separator picks out the few product nuclei from the much more intense beam.", "details": "St. George (Strong Gradient Electromagnetic Online Recoil separator for capture Gamma Ray Experiments) was designed for (α,γ) reactions in inverse kinematics with beams up to about A = 40, with an angular acceptance of 40 mrad and an energy acceptance of 7.4%.", "refs": [ "couder2008" ] }, { "id": "tunl-lena", "name": "LENA, TUNL", "lab": "Triangle Universities Nuclear Laboratory", "location": "Durham, North Carolina", "country": "United States", "underground": false, "accelerator": "230 kV ECR accelerator and 1 MV JN Van de Graaff; a 2 MV Singletron was added in the LENA II upgrade", "url": "https://tunl.duke.edu/nuclear-astrophysics/lena-accelerators", "summary": "The Laboratory for Experimental Nuclear Astrophysics, a low-energy, high-current accelerator facility at the surface. It uses detector arrays with active shielding against cosmic rays to measure weak proton-capture resonances." }, { "id": "dragon", "name": "DRAGON, TRIUMF", "lab": "TRIUMF", "location": "Vancouver, British Columbia", "country": "Canada", "underground": false, "summary": "The Detector of Recoils And Gammas Of Nuclear reactions, a recoil separator at the radioactive-beam facility of TRIUMF. It measures radiative captures in inverse kinematics, including captures on short-lived nuclei that cannot be made into targets.", "details": "DRAGON has a windowless gas target surrounded by a γ-ray detector array, an electromagnetic recoil mass separator and focal-plane detectors. It was commissioned with stable and radioactive beams from ISAC; its first radioactive-beam study was ²¹Na(p,γ)²²Mg.", "refs": [ "hutcheon2003" ] }, { "id": "erna", "name": "ERNA recoil separator", "lab": "CIRCE laboratory, Caserta (at Ruhr-Universität Bochum until 2009)", "location": "Caserta", "country": "Italy", "underground": false, "accelerator": "recoil separator, first on the Bochum 4 MV Dynamitron, since 2009 at CIRCE", "summary": "The European Recoil separator for Nuclear Astrophysics, built to measure helium-capture reactions such as ¹²C(α,γ)¹⁶O in inverse kinematics by counting the product nuclei directly.", "details": "ERNA was built at the 4 MV Dynamitron in Bochum to detect ¹⁶O recoils from ¹²C(α,γ)¹⁶O. Wien filters before and after the analysing magnet reduced the ¹⁶O contamination of the ¹²C beam from about 10⁻¹¹ to below 2 × 10⁻²⁹. In 2009 the separator moved to the CIRCE laboratory in Caserta, where a charge-state selection dipole was added directly after the target.", "refs": [ "rogalla1999", "schurmann2005", "broggini2019" ] }, { "id": "kellogg", "name": "Kellogg Radiation Laboratory, Caltech", "lab": "California Institute of Technology", "location": "Pasadena, California", "country": "United States", "underground": false, "summary": "The laboratory where William Fowler and colleagues measured many of the reactions that power stars. Salpeter's work on the triple-alpha process (1951) and the measurements of the Hoyle state (1953, 1957) were done here.", "refs": [ "salpeter1952", "dunbar1953", "cook1957", "fowler1984" ] }, { "id": "atomki", "name": "Atomki, Debrecen", "lab": "Institute for Nuclear Research (Atomki)", "location": "Debrecen", "country": "Hungary", "underground": false, "summary": "A nuclear research institute with several accelerators. Its astrophysics group is known for activation measurements, in which the cross section is found by counting the decays of the radioactive product after the irradiation.", "refs": [ "gyurky2023" ] }, { "id": "lns-catania", "name": "INFN LNS, Catania", "lab": "Laboratori Nazionali del Sud (INFN)", "location": "Catania", "country": "Italy", "underground": false, "summary": "An INFN national laboratory with a tandem accelerator and a superconducting cyclotron. Many Trojan Horse experiments have been done here." }, { "id": "texas-am", "name": "Cyclotron Institute, Texas A&M", "lab": "Texas A&M University", "location": "College Station, Texas", "country": "United States", "underground": false, "summary": "A university cyclotron laboratory where many transfer-reaction measurements of asymptotic normalization coefficients (ANCs) were made for capture reactions of astrophysical interest." }, { "id": "n-tof", "name": "n_TOF, CERN", "lab": "CERN", "location": "Geneva", "country": "Switzerland", "underground": false, "accelerator": "20 GeV/c proton beam from the CERN PS on a lead spallation target", "years": "in operation since 2001", "summary": "A neutron source at CERN in which protons from an accelerator strike a lead target and knock out neutrons with a wide range of energies. The energy of each neutron is found from its time of flight along a long beam line. It measures neutron captures for the s- and r-processes and neutron-induced reactions on light nuclei.", "details": "Pulses of up to 8.5 × 10¹² protons, 6 ns (rms) long, strike the lead target. The horizontal flight path to experimental area EAR1 is 185 m; a second area, EAR2, sits about 20 m above the target on a vertical flight path. A nitrogen-cooled third-generation target was installed during the CERN Long Shutdown 2 (2019–2021).", "refs": [ "guerrero2013" ] }, { "id": "nif", "name": "National Ignition Facility", "lab": "Lawrence Livermore National Laboratory", "location": "Livermore, California", "country": "United States", "underground": false, "summary": "A large laser system built for inertial-confinement fusion. Its lasers compress small capsules of fuel into a hot, dense plasma, in which fusion reactions between light nuclei can be studied in conditions closer to those in stars than an accelerator beam on a cold target." }, { "id": "stuttgart-dynamitron", "name": "Dynamitron, Stuttgart", "lab": "Institut für Strahlenphysik, Universität Stuttgart", "location": "Stuttgart", "country": "Germany", "underground": false, "accelerator": "Dynamitron", "summary": "A university accelerator laboratory where ¹²C(α,γ)¹⁶O, among other helium-capture reactions, was measured with γ-ray detectors." }, { "id": "karlsruhe-vdg", "name": "Karlsruhe Van de Graaff", "lab": "Kernforschungszentrum Karlsruhe (now Karlsruhe Institute of Technology)", "location": "Karlsruhe", "country": "Germany", "underground": false, "accelerator": "single-ended Van de Graaff (3.7 MV)", "summary": "A Van de Graaff accelerator at the Karlsruhe nuclear research centre, used for measurements of ¹²C(α,γ)¹⁶O and, for decades, of the neutron captures of the s-process. Protons on a lithium target there make neutrons whose energies mimic those in a star, and many of the stellar capture rates in use today were measured with them.", "details": "Protons of 1912 keV, just above the ⁷Li(p,n)⁷Be threshold, give a forward-collimated neutron spectrum that closely resembles a Maxwell–Boltzmann distribution at kT = 25 keV; a sample in the cone is activated, and the ⁷Be activity of the target gives the integrated flux (Beer and Käppeler 1980; Ratynski and Käppeler 1988). With a pulsed beam the same machine served time-of-flight measurements with the Karlsruhe 4π BaF₂ array, 42 crystals forming a spherical shell of 10 cm inner radius and 15 cm thickness (Wisshak et al. 2006).", "refs": [ "beer1980", "ratynski1988", "wisshak2006" ] }, { "id": "tunl-tandem", "name": "TUNL tandem", "lab": "Triangle Universities Nuclear Laboratory", "location": "Durham, North Carolina", "country": "United States", "underground": false, "accelerator": "tandem Van de Graaff", "summary": "The tandem accelerator of the Triangle Universities Nuclear Laboratory, run by Duke University, the University of North Carolina and North Carolina State University. LENA, the low-energy laboratory, is part of the same institute." }, { "id": "jsi-ljubljana", "name": "Jožef Stefan Institute", "lab": "Jožef Stefan Institute", "location": "Ljubljana", "country": "Slovenia", "underground": false, "summary": "A research institute in Ljubljana whose accelerator laboratory has measured proton captures on light nuclei at low energy." }, { "id": "rcnp-osaka", "name": "RCNP, Osaka", "lab": "Research Center for Nuclear Physics, Osaka University", "location": "Ibaraki, Osaka", "country": "Japan", "underground": false, "summary": "A university centre for nuclear physics with cyclotrons for nuclear structure and reactions. The OCEAN low-energy set-up measured ³He + ³He fusion here." }, { "id": "omega", "name": "OMEGA laser", "lab": "Laboratory for Laser Energetics, University of Rochester", "location": "Rochester, New York", "country": "United States", "underground": false, "summary": "A high-power laser that compresses small fuel capsules for inertial-confinement fusion research. Fusion of light nuclei in its implosions has been studied as a plasma counterpart of accelerator measurements." }, { "id": "weizmann", "name": "Weizmann Institute accelerator laboratory", "lab": "Weizmann Institute of Science", "location": "Rehovot", "country": "Israel", "underground": false, "summary": "The accelerator laboratory of the Weizmann Institute, where ³He(α,γ)⁷Be, the reaction that makes the ⁷Be of the Sun, was measured." }, { "id": "cenpa", "name": "CENPA, University of Washington", "lab": "Center for Experimental Nuclear Physics and Astrophysics, University of Washington", "location": "Seattle, Washington", "country": "United States", "underground": false, "accelerator": "tandem Van de Graaff", "summary": "A university laboratory in Seattle with a tandem accelerator, where ³He(α,γ)⁷Be was measured for the solar neutrino fluxes." }, { "id": "oslo-ocl", "name": "Oslo Cyclotron Laboratory", "lab": "University of Oslo", "location": "Oslo", "country": "Norway", "underground": false, "accelerator": "cyclotron", "summary": "A university cyclotron laboratory in Oslo, used for light-ion reactions and γ-ray decay studies of excited nuclear states." }, { "id": "isolde", "name": "ISOLDE, CERN", "lab": "CERN", "location": "Geneva", "country": "Switzerland", "underground": false, "summary": "CERN's facility for radioactive nuclei. Protons strike thick targets, and the short-lived nuclei produced are separated by mass and delivered as low-energy or post-accelerated beams." }, { "id": "anu", "name": "Heavy Ion Accelerator Facility, ANU", "lab": "Australian National University", "location": "Canberra", "country": "Australia", "underground": false, "accelerator": "tandem electrostatic accelerator", "summary": "The heavy-ion accelerator laboratory of the Australian National University, used for nuclear structure and reaction studies." }, { "id": "circe", "name": "CIRCE, Caserta", "lab": "Center for Isotopic Research on Cultural and Environmental heritage (Università della Campania and INNOVA)", "location": "Caserta", "country": "Italy", "underground": false, "summary": "An accelerator laboratory in Caserta built for isotope analysis. Since 2009 it has also hosted the ERNA recoil separator for helium-capture measurements.", "refs": [ "broggini2019" ] }, { "id": "andromede", "name": "Andromède, Orsay", "lab": "Institut de Physique Nucléaire d'Orsay (IPN Orsay)", "location": "Orsay", "country": "France", "underground": false, "summary": "An accelerator at Orsay that hosts STELLA, a station built to measure the fusion of light nuclei such as carbon with carbon at very low energies, where the reaction is extremely rare.", "details": "STELLA combines a silicon array for the charged particles with LaBr₃ detectors of the UK FATIMA array for the γ-rays, with nanosecond timing that separates protons from α particles, and a rotating target that withstands beam currents above 10 µA. It is designed for cross sections down to tens of picobarns.", "refs": [ "heine2018" ] }, { "id": "csnsm-orsay", "name": "CSNSM, Orsay", "lab": "Centre de Sciences Nucléaires et de Sciences de la Matière (CNRS/IN2P3 and Université Paris-Sud), since 2020 part of IJCLab", "location": "Orsay", "country": "France", "underground": false, "summary": "A laboratory near Paris with low-energy accelerators and an ion implanter. Proton captures on radioactive ⁷Be targets and on ¹⁷O were measured here.", "refs": [ "hammache2001", "chafa2005" ] }, { "id": "cenbg", "name": "CENBG, Bordeaux-Gradignan", "lab": "Centre d'Études Nucléaires de Bordeaux Gradignan (CNRS/IN2P3)", "location": "Gradignan, Bordeaux", "country": "France", "underground": false, "accelerator": "Van de Graaff", "summary": "A nuclear physics laboratory near Bordeaux. Its Van de Graaff accelerator was used for one of the direct measurements of ⁷Be(p,γ)⁸B with a radioactive target.", "refs": [ "hammache1998" ] }, { "id": "riken", "name": "RIKEN, Wako", "lab": "RIKEN (today the RIKEN Nishina Center for Accelerator-Based Science)", "location": "Wako, Saitama", "country": "Japan", "underground": false, "summary": "A Japanese national research institute whose accelerators make beams of short-lived nuclei by fragmenting heavier ones in flight. The first Coulomb-dissociation measurement of ⁸B was done here with the RIPS fragment separator.", "refs": [ "motobayashi1994" ] }, { "id": "gsi", "name": "GSI, Darmstadt", "lab": "GSI Helmholtzzentrum für Schwerionenforschung", "location": "Darmstadt", "country": "Germany", "underground": false, "summary": "A heavy-ion accelerator laboratory. Its fragment separator delivers fast beams of short-lived nuclei, which were used to measure the Coulomb dissociation of ⁸B and the break-up of ⁶Li.", "refs": [ "schumann2006", "hammache2010" ] }, { "id": "gelina", "name": "GELINA, Geel", "lab": "Joint Research Centre (JRC), European Commission", "location": "Geel", "country": "Belgium", "underground": false, "accelerator": "pulsed electron linear accelerator; measurement stations 10 to 400 m from the neutron source", "url": "https://joint-research-centre.ec.europa.eu/laboratories-z/jrc-neutron-time-flight-facility_en", "summary": "A neutron time-of-flight facility of the European Commission. Short bursts of electrons make bursts of neutrons of every energy from thermal to about 20 MeV, and the time each neutron takes to reach a sample gives its energy. It measures neutron cross sections for nuclear data and for astrophysics, ¹⁹⁷Au(n,γ) among them.", "details": "The electron pulses are compressed to about 1 ns; up to ten experiments run at once on flight paths between 10 and 400 m, covering neutron energies from 10 meV to 20 MeV.", "refs": [ "massimi2014" ] }, { "id": "lansce-dance", "name": "DANCE at LANSCE", "lab": "Los Alamos Neutron Science Center, Los Alamos National Laboratory", "location": "Los Alamos, New Mexico", "country": "United States", "underground": false, "accelerator": "800 MeV protons on a tungsten spallation target (Lujan Center); DANCE on a 20 m flight path", "summary": "The Detector for Advanced Neutron Capture Experiments: a ball of barium fluoride crystals that surrounds a tiny sample and catches nearly every γ-ray emitted when it captures a neutron. Because the sample can weigh as little as a milligram, it can be radioactive, which is what branch points of the s-process need.", "details": "Up to 160 BaF₂ crystals form a 4π shell of about 17 cm inner radius and 15 cm thickness; samples down to about 1 mg, or with activities up to about 1 Ci, can be measured. Neutron energies come from the time of flight.", "refs": [ "weigand2015" ] }, { "id": "franz", "name": "FRANZ, Frankfurt", "lab": "Stern-Gerlach-Zentrum, Goethe-Universität Frankfurt", "location": "Frankfurt am Main", "country": "Germany", "underground": false, "accelerator": "Van de Graaff for ⁷Li(p,n) activations; a high-current RFQ–IH proton linac (about 2 MeV) under construction", "summary": "The Frankfurt Neutron Source, designed to be the most intense source of neutrons at the energies found in stars, about a thousand times more intense than the Karlsruhe source in that energy range. Like Karlsruhe, it makes the neutrons from protons on lithium.", "refs": [ "reifarth2009" ] }, { "id": "saraf-lilit", "name": "SARAF and LiLiT", "lab": "Soreq Nuclear Research Center", "location": "Yavne", "country": "Israel", "underground": false, "accelerator": "superconducting proton linac (SARAF) on a liquid-lithium target (LiLiT), 1.9 MeV, 1–2 mA", "summary": "A proton accelerator whose milliampere beam strikes a flowing film of liquid lithium, making neutrons with a spectrum close to that of a star at 30 keV, more than ten times more intensely than earlier lithium targets. Samples are activated and their radioactivity counted.", "details": "The thick-target ⁷Li(p,n)⁷Be spectrum at 1.92 MeV is quasi-Maxwellian with kT ≈ 30 keV; 3–5 × 10¹⁰ n/s were reached in the first experiments, which measured the 30 keV MACS of ⁹⁴Zr and ⁹⁶Zr (Tessler et al. 2015).", "refs": [ "tessler2015" ] } ], "methods": [ { "id": "direct-underground", "name": "Direct measurement underground", "summary": "An accelerator in a laboratory deep underground fires a beam at a target, and detectors count the products of the reaction. The rock above stops most cosmic rays, so the detectors can see reactions that happen only a few times per day, at energies close to those inside stars.", "details": "The observable is the reaction yield per incident projectile, measured with γ-ray or charged-particle detectors as a function of beam energy. The cross section, or the resonance strength for narrow resonances, follows from the yield, the target stoichiometry and thickness, the stopping power and the detection efficiency. Underground, the muon flux and the muon-induced γ-ray and neutron backgrounds are reduced by orders of magnitude, which lowers the minimum measurable yield. The remaining background comes from the environmental radioactivity of the rock and of the set-up, and from beam-induced reactions on target contaminants. Typical systematic limits are the beam current integration, the target thickness and its degradation under beam, the effective interaction energy in a thick or degrading target, the γ-ray detection efficiency including summing and angular distributions, and electron screening at the lowest energies.", "strengths": [ "Measures the reaction of interest directly, without a nuclear model.", "Reaches energies inside or near the Gamow window for many hydrogen-burning reactions.", "Low background allows long runs on very small cross sections." ], "limits": [ "Only a few facilities exist, and beam time is limited.", "At the lowest energies the yield is still small and statistics dominate.", "Laboratory data include electron screening, which differs from that in a stellar plasma.", "Below the lowest measured energy an extrapolation, usually by R-matrix, is still needed." ], "refs": [ "broggini2010", "broggini2018", "junker2023" ], "examples": [ "3He-3He2p-4He", "14N-pg-15O", "2H-pg-3He" ] }, { "id": "direct-surface", "name": "Direct measurement at the surface", "summary": "The same kind of experiment in an ordinary laboratory above ground. It covers a much wider range of energies and beams, but cosmic rays limit how small a cross section can be measured.", "details": "Yields are measured as underground, but the background from cosmic-ray muons and their secondaries limits the sensitivity for γ-ray energies up to several MeV unless active or passive shielding is used. Surface data usually fix the higher-energy part of the excitation function, the resonance energies and widths, and the γ-ray branchings and angular distributions that an R-matrix fit needs. They are often the main input for the extrapolation into the Gamow window. Systematic limits are the same as underground, with background subtraction added.", "strengths": [ "Wide choice of accelerators, beams and energies.", "Supplies angular distributions, branchings and the high-energy data that constrain R-matrix fits." ], "limits": [ "Cosmic-ray background limits the lowest measurable cross section.", "Low-energy data rely on extrapolation." ], "refs": [ "fowler1984", "deboer2017" ], "examples": [ "12C-ag-16O", "14N-pg-15O" ] }, { "id": "inverse-kinematics", "name": "Inverse kinematics and recoil separators", "summary": "The roles of beam and target are swapped: a heavy beam hits a light target such as hydrogen or helium gas. The product nuclei fly forward with the beam, and a recoil separator picks them out and counts them.", "details": "In a radiative capture A(a,γ)B studied as a(A,γ)B, the recoil B leaves the target inside a narrow forward cone. An electromagnetic separator suppresses the unreacted beam by many orders of magnitude, and the recoils are identified at the focal plane, often in coincidence with the capture γ-rays. The method measures the total capture cross section with no need for a γ-ray efficiency model, and it works with radioactive beams. Systematic limits are the separator acceptance and transmission, the charge-state distribution of the recoils, the beam suppression, and the gas-target density and beam normalization.", "strengths": [ "Gives the total cross section directly, independent of the γ-ray cascade.", "Works with short-lived beams that cannot be made into targets." ], "limits": [ "The recoil cone must fit the separator acceptance, which restricts reactions and energies.", "Beam leaking through the separator limits the lowest measurable yield.", "Charge-state fractions must be measured or modelled." ], "refs": [ "schurmann2005", "hutcheon2003", "couder2008" ], "examples": [ "12C-ag-16O", "3He-ag-7Be" ] }, { "id": "activation", "name": "Activation", "summary": "When the reaction product is radioactive, the target is irradiated and then moved to a low-background counting station. The number of decays gives the number of reactions.", "details": "The number of product nuclei is inferred from their decay radiation, measured offline, together with the half-life and the decay branching. The method gives the total cross section, summed over all γ-ray cascades and integrated over angle, which avoids the summing and angular corrections of prompt γ-ray spectroscopy. Long-lived products can also be counted atom by atom with accelerator mass spectrometry. Systematic limits are the decay data, the counting efficiency, the irradiation history and the loss of product nuclei from the target.", "strengths": [ "Total cross section, independent of the γ-ray cascade and angular distribution.", "Counting can be done in a low-background setting away from the beam." ], "limits": [ "Needs a radioactive product with a suitable half-life.", "Gives no information on individual transitions." ], "refs": [ "gyurky2007", "gyurky2023" ], "examples": [ "3He-ag-7Be", "12C-pg-13N", "25Mg-pg-26Al" ] }, { "id": "neutron-beams", "name": "Neutron beams and time of flight", "summary": "Neutrons with a wide range of energies are produced in short bursts. The time a neutron takes to reach the sample tells its energy, so one experiment measures the cross section at many energies.", "details": "At spallation or photoneutron sources the neutron energy is found from the flight time over a known path. Capture is measured with γ-ray detectors and charged-particle reactions with silicon or gas detectors. Maxwellian-averaged cross sections at stellar temperatures are then computed from the energy-dependent data. Systematic limits include the neutron flux shape, the sample mass, the detector response and backgrounds from scattered neutrons.", "strengths": [ "Covers many energies in one measurement.", "Applies to neutron captures and to neutron-induced reactions on radioactive samples." ], "limits": [ "Requires a sample of the target nucleus, which is hard for short-lived nuclei.", "The neutron flux must be known over the whole energy range." ], "refs": [ "guerrero2013" ], "examples": [ "7Be-np-7Li" ] }, { "id": "thm", "name": "Trojan Horse method", "summary": "An indirect method in which the interesting nucleus is carried inside a larger one, the Trojan horse, at an energy above the Coulomb barrier. The reaction with the carried nucleus can then be studied at very low effective energies.", "details": "A two-body reaction A + x → c + C at sub-Coulomb energy is studied through a three-body reaction A + a → c + C + s, where a has a large x + s cluster structure and s acts as a spectator. In quasi-free kinematics the measured three-body cross section is factorised into a kinematic factor, the momentum distribution of x inside a, and the half-off-energy-shell two-body cross section. The method gives the energy dependence of the bare-nucleus cross section without Coulomb suppression or electron screening; its absolute scale is normalized to direct data at higher energies. Systematic limits are the validity of the quasi-free factorisation, the momentum distribution adopted, the off-shell corrections and the normalization.", "strengths": [ "Reaches energies far below those accessible directly, free of electron screening.", "Applicable to charged-particle-induced and to neutron-induced reactions." ], "limits": [ "Requires normalization to direct data.", "Depends on the quasi-free reaction model and its assumptions." ], "refs": [ "tumino2021", "tribble2014" ], "examples": [ "2H-dp-3H", "19F-pa-16O", "18O-pa-15N", "13C-an-16O" ] }, { "id": "anc", "name": "Transfer reactions and ANCs", "summary": "At very low energy, capture happens at large distances from the nucleus, where only the tail of the final-state wave function matters. A transfer reaction at higher energy can measure the size of that tail, which then gives the low-energy capture rate.", "details": "The asymptotic normalization coefficient (ANC) fixes the amplitude of the bound-state wave function outside the nuclear interior. For peripheral transfer reactions, measured at energies where the cross section is large, the ANC can be extracted with much smaller dependence on the optical-model and single-particle parameters than a spectroscopic factor. The ANC then determines the external direct-capture contribution and the contribution of subthreshold states in an R-matrix calculation. Systematic limits are the optical potentials, the peripherality of the reaction and the reaction model (DWBA or coupled channels).", "strengths": [ "Gives low-energy direct capture and subthreshold-state contributions without measuring the capture itself.", "Uses reactions with large cross sections." ], "limits": [ "Model dependent through the optical potentials and the reaction theory.", "Covers only the non-resonant and subthreshold parts of the rate." ], "refs": [ "tribble2014" ], "examples": [ "14N-pg-15O", "7Be-pg-8B", "12C-ag-16O" ] }, { "id": "lifetime", "name": "Lifetimes of excited states", "summary": "Not a measurement of the reaction itself, but of one ingredient of it. How long an excited state of the product nucleus lives fixes how strongly it takes part in the capture. Very short lifetimes are measured from how much the emitted γ-rays are shifted by the Doppler effect while the recoiling nucleus slows down in the target.", "details": "In the Doppler-shift attenuation method (DSAM) the nucleus is populated by a reaction that gives it a known recoil velocity, and the γ-ray energy is measured while the nucleus slows down in the target or backing. The attenuation of the full Doppler shift, compared with the stopping power, gives lifetimes from about 1 fs to 1 ps. The radiative width that follows enters an R-matrix fit of the capture, for example for a subthreshold state whose tail reaches into the Gamow window. Systematic limits are the stopping powers, which are known to a few per cent at best, and the sensitivity at the shortest lifetimes, where the attenuation is nearly complete.", "strengths": [ "Constrains the width of a state that cannot be reached directly at low energy.", "Independent of the capture cross section and its normalization." ], "limits": [ "Depends on stopping powers.", "Lifetimes below about a femtosecond are hard to resolve." ], "refs": [ "bertone2001", "schurmann2008" ], "examples": [ "14N-pg-15O" ] }, { "id": "coulomb-dissociation", "name": "Coulomb dissociation", "summary": "The time-reverse of a capture. A fast beam of the product nucleus passes close to a heavy target, and the strong electric field breaks it apart. From the break-up rate the capture cross section can be calculated.", "details": "Baur, Bertulani and Rebel proposed the method in 1986. The virtual photons of the Coulomb field of a high-Z target induce the photodissociation B + γ → A + a, which is related to the capture A(a,γ)B by detailed balance. The dissociation cross section is large because of the high virtual-photon flux, and radioactive beams can be used. Systematic limits are the contributions of nuclear break-up, of higher multipoles (E2 in an E1-dominated case), of post-acceleration in the Coulomb field, and the reaction model used to extract the photodissociation cross section.", "strengths": [ "Large cross sections and the use of radioactive beams.", "Low relative energies between the fragments are accessible." ], "limits": [ "Depends on the reaction model and on multipole separation.", "Nuclear and higher-order Coulomb effects must be subtracted." ], "refs": [ "baur1986", "tribble2014" ], "examples": [ "7Be-pg-8B" ] }, { "id": "plasma", "name": "Laser and inertial-confinement plasmas", "summary": "Lasers compress and heat a small capsule of fuel until the nuclei fuse. The reactions then take place in a hot plasma, as they do in stars, rather than between a beam and a cold target.", "details": "Reaction yields are measured from the emitted neutrons, charged particles or γ-rays, and the plasma temperature and density are inferred from other diagnostics. The method samples the thermally averaged reactivity directly and can test plasma effects such as screening. Systematic limits are the knowledge of the plasma conditions, which vary in space and time, and the separation of the reaction of interest from other reactions in the fuel. At the National Ignition Facility, Casey et al. measured the ²H(d,n)³He and ³H(t,2n)⁴He S-factors in implosions at temperatures of 2.1–5.4 keV and densities of 1.2–16 g cm⁻³, in agreement with accelerator data within the uncertainties.", "strengths": [ "Probes reactions in a thermal plasma.", "Allows studies of reactions between radioactive light nuclei such as tritium." ], "limits": [ "Plasma conditions are known only approximately.", "Limited so far to fusion of the lightest nuclei." ], "refs": [ "casey2017", "zylstra2017" ], "examples": [ "3H-dn-4He", "2H-dn-3He" ] }, { "id": "photonuclear", "name": "Photonuclear reactions", "summary": "When the target of a neutron capture is too radioactive to make into a sample, the reaction can be studied backwards: γ-rays knock a neutron out of the product nucleus, and what that reveals about the nucleus is used to calculate the capture.", "details": "Monoenergetic, polarized photon beams from laser Compton backscattering, such as HIγS at the Triangle Universities Nuclear Laboratory, measure the (γ,n) cross section of the capture product from the neutron separation energy upwards; with (γ,γ′) data below it they fix the γ-ray strength function, the main uncertainty of statistical-model capture cross sections. The result is a constrained calculation, not a measurement of the capture itself; the ⁸⁵Kr branch point is an example (Raut et al. 2013).", "strengths": [ "Needs no radioactive sample of the capturing nucleus.", "Constrains the γ-ray strength, the weakest input of the statistical model." ], "limits": [ "Gives the capture cross section only through a model.", "Probes the product nucleus, not the stellar reaction at stellar energies." ], "refs": [ "raut2013" ], "examples": [ "85Kr-ng-86Kr" ] }, { "id": "theory", "name": "Calculation from theory", "summary": "Some rates cannot be measured at all at stellar energies and are calculated instead. The weak proton–proton fusion that starts the Sun's energy production is the main example.", "details": "For weak-interaction processes such as p + p → d + e⁺ + ν the cross section is too small for any laboratory measurement and is computed from nuclear theory. For radiative captures and resonant reactions, R-matrix and microscopic models extrapolate measured data to stellar energies. Electron capture rates in the solar plasma also come from theory.", "strengths": [ "The only source for some weak-interaction rates.", "Provides the energy dependence that links measured data to stellar energies." ], "limits": [ "Accuracy depends on the nuclear model and its inputs.", "Extrapolations need data to constrain them." ], "refs": [ "bethe1938", "adelberger2011", "acharya2025" ], "examples": [ "1H-pp-2H", "1H-pep-2H", "7Be-ec-7Li" ] } ], "timeline": [ { "id": "1920-eddington-proposes-that-stars-burn-hydrogen", "year": 1920, "month": 8, "url": null, "title": "Eddington proposes that stars burn hydrogen into helium", "text": "In an address to the British Association in Cardiff, Arthur Eddington noted that a helium nucleus weighs less than four hydrogen nuclei. He argued that the mass lost when hydrogen turns into helium inside stars would be released as energy, enough to keep them shining for a very long time. How this could happen was not yet known.", "categories": [ "theory" ], "luna": false, "reactions": [], "refs": [ "eddington1920" ], "facility": null, "highlight": true }, { "id": "1928-gamow-explains-how-particles-cross-the", "year": 1928, "month": null, "url": null, "title": "Gamow explains how particles cross the Coulomb barrier", "text": "George Gamow used the new quantum mechanics to explain alpha decay. A particle can pass through the electric repulsion between nuclei, the Coulomb barrier, even when its energy is too low to climb over it. This effect, called tunnelling, is what makes nuclear fusion possible in stars.", "categories": [ "theory" ], "luna": false, "reactions": [], "refs": [ "gamow1928" ], "facility": null, "highlight": true }, { "id": "1929-atkinson-and-houtermans-apply-tunnelling-to", "year": 1929, "month": null, "url": null, "title": "Atkinson and Houtermans apply tunnelling to the stars", "text": "Robert Atkinson and Fritz Houtermans used Gamow's result to estimate how often light nuclei fuse at the temperatures inside stars. They found that tunnelling makes such reactions frequent enough to power a star. Their paper is often taken as the start of nuclear astrophysics.", "categories": [ "theory" ], "luna": false, "reactions": [], "refs": [ "atkinson1929" ], "facility": null, "highlight": false }, { "id": "1938-von-weizsacker-and-the-carbon-nitrogen", "year": 1938, "month": null, "url": null, "title": "Von Weizsäcker and the carbon–nitrogen cycle", "text": "In two papers in Physikalische Zeitschrift, Carl Friedrich von Weizsäcker discussed which nuclear reactions could power stars. The second paper proposed a cycle in which carbon and nitrogen nuclei help turn hydrogen into helium and are given back at the end. His notes and letters show that after he turned to fission and war research in 1939 he kept thinking about neutron stars and cosmology.", "categories": [ "theory" ], "luna": false, "reactions": [], "refs": [ "weizsacker1937", "weizsacker1938", "wiescher2025" ], "facility": null, "highlight": false }, { "id": "1938-bethe-and-critchfield-describe-proton-proton", "year": 1938, "month": 8, "url": null, "title": "Bethe and Critchfield describe proton–proton fusion", "text": "Hans Bethe and Charles Critchfield calculated the rate at which two protons fuse into a deuteron, emitting a positron and a neutrino. This very slow weak-interaction process is the first step of the proton–proton chain that powers the Sun.", "categories": [ "theory" ], "luna": false, "reactions": [ "1H-pp-2H" ], "refs": [ "bethe1938" ], "facility": null, "highlight": false }, { "id": "1939-bethe-works-out-the-cn-cycle", "year": 1939, "month": 3, "url": null, "title": "Bethe works out the CN cycle in “Energy production in stars”", "text": "Hans Bethe worked out the carbon–nitrogen cycle in detail and estimated its rate. He concluded that carbon and nitrogen act as catalysts that fuse protons into helium in stars. Together with the proton–proton chain, this is still the basis of how we understand hydrogen burning.", "categories": [ "theory" ], "luna": false, "reactions": [ "12C-pg-13N", "14N-pg-15O", "15N-pa-12C" ], "refs": [ "bethe1939" ], "facility": null, "highlight": true }, { "id": "1946-los-alamos-finds-atmospheric-ignition-very", "year": 1946, "month": null, "url": null, "title": "Los Alamos finds atmospheric ignition very unlikely", "text": "In 1942 Edward Teller had asked whether a fission bomb could start nitrogen burning in the air. Hans Bethe judged the chance very low, and in 1946 Emil Konopinski, Cloyd Marvin and Teller found that, under their assumptions, the energy lost to radiation always exceeds the energy gained from the fusion of two nitrogen-14 nuclei; they still asked for further work. At Notre Dame, secret accelerator experiments of the 1940s studied how efficiently the air cools the fireball of a nuclear explosion. The experience gained fed into post-war nuclear astrophysics.", "categories": [ "theory", "experiment" ], "luna": false, "reactions": [], "refs": [ "konopinski1946", "wiescher2024pt", "wiescher2024cool" ], "facility": null, "highlight": false }, { "id": "1948-alpher-bethe-and-gamow-on-the", "year": 1948, "month": 4, "url": null, "title": "Alpher, Bethe and Gamow on the hot early Universe", "text": "Ralph Alpher and George Gamow proposed that the light elements formed in the first moments of a hot, expanding Universe. Gamow added Bethe's name so that the authors read like the first three Greek letters. The idea became Big Bang nucleosynthesis, although heavier elements turned out to be made in stars.", "categories": [ "theory" ], "luna": false, "reactions": [ "1H-ng-2H" ], "refs": [ "alpher1948" ], "facility": null, "highlight": false }, { "id": "1952-salpeter-shows-how-helium-burns-to", "year": 1952, "month": null, "url": null, "title": "Salpeter shows how helium burns to carbon", "text": "Edwin Salpeter showed how helium can burn in red giant stars. Two helium nuclei form unstable ⁸Be, which lives just long enough to capture a third helium nucleus and become carbon. He did this work at Caltech's Kellogg Radiation Laboratory, with William Fowler, in the summer of 1951.", "categories": [ "theory" ], "luna": false, "reactions": [ "4He-aa-12C" ], "refs": [ "salpeter1952" ], "facility": null, "highlight": false }, { "id": "1952-technetium-is-found-in-red-giants", "year": 1952, "month": null, "url": null, "title": "Technetium is found in red giants", "text": "Paul Merrill found lines of technetium in the spectra of red giants of class S. Technetium has no stable isotope, and even its longest-lived ones last only a few million years, far less than the age of these stars. It must have been made inside them: the first direct evidence that stars build elements, by the slow neutron captures of the s-process.", "categories": [ "observation" ], "luna": false, "reactions": [], "refs": [ "merrill1952", "kaeppeler2011" ], "facility": null, "highlight": false }, { "id": "1953-the-7-68-mev-state-of", "year": 1953, "month": 11, "url": null, "title": "The 7.68 MeV state of carbon-12 is found", "text": "At Caltech, Dunbar, Pixley, Wenzel and Whaling found an excited state of ¹²C at 7.68 ± 0.03 MeV in the reaction ¹⁴N(d,α)¹²C. Fred Hoyle had pointed out that such a state would make the triple-alpha process fast enough to produce the carbon we see. It is now called the Hoyle state.", "categories": [ "experiment" ], "luna": false, "reactions": [ "4He-aa-12C" ], "refs": [ "dunbar1953" ], "facility": null, "highlight": false }, { "id": "1954-hoyle-on-the-synthesis-of-elements", "year": 1954, "month": null, "url": null, "title": "Hoyle on the synthesis of elements in hot stars", "text": "Fred Hoyle argued that the elements from carbon to nickel are made at the high temperatures reached inside massive stars late in their lives. The paper set out the idea that stars, not the Big Bang, made most of the elements.", "categories": [ "theory" ], "luna": false, "reactions": [], "refs": [ "hoyle1954" ], "facility": null, "highlight": false }, { "id": "1957-cook-fowler-and-the-lauritsens-confirm", "year": 1957, "month": null, "url": null, "title": "Cook, Fowler and the Lauritsens confirm the Hoyle state", "text": "At the Kellogg Radiation Laboratory, Cook, Fowler, C. C. Lauritsen and T. Lauritsen studied the decay of ¹²B to the 7.65 MeV state of ¹²C and its break-up into three alpha particles. They concluded that the state can act as the resonance Hoyle needed for helium burning in red giants.", "categories": [ "experiment" ], "luna": false, "reactions": [ "4He-aa-12C" ], "refs": [ "cook1957" ], "facility": null, "highlight": false }, { "id": "1957-cameron-s-lectures-on-nucleogenesis", "year": 1957, "month": 6, "url": null, "title": "Cameron's lectures on nucleogenesis", "text": "Alastair Cameron, at Chalk River in Canada, published an independent account of how the elements are made in stars. Among other results he named the two reactions that supply neutrons for slow neutron capture, ¹³C(α,n)¹⁶O and ²²Ne(α,n)²⁵Mg.", "categories": [ "theory" ], "luna": false, "reactions": [ "13C-an-16O", "22Ne-an-25Mg" ], "refs": [ "cameron1957" ], "facility": null, "highlight": false }, { "id": "1957-the-b2fh-paper", "year": 1957, "month": 10, "url": null, "title": "The B²FH paper", "text": "Margaret Burbidge, Geoffrey Burbidge, William Fowler and Fred Hoyle published a 104-page review of how the elements are made in stars. It sorted the processes by the nuclear reactions involved, including slow and rapid neutron capture, and compared them with the measured Solar System abundances. It is known by the authors' initials, B²FH.", "categories": [ "theory" ], "luna": false, "reactions": [], "refs": [ "b2fh1957" ], "facility": null, "highlight": true }, { "id": "1961-the-s-process-as-a-chain", "year": 1961, "month": null, "url": null, "title": "The s-process as a chain of neutron captures", "text": "Donald Clayton, William Fowler, Thomas Hull and Barbara Zimmerman worked out how abundances build up along a long chain of slow neutron captures and compared the result with the observed abundances of the heavy elements, for the slow process that B²FH had named.", "categories": [ "theory" ], "luna": false, "reactions": [], "refs": [ "clayton1961" ], "facility": null, "highlight": false }, { "id": "1964-bahcall-proposes-a-solar-neutrino-experiment", "year": 1964, "month": null, "url": null, "title": "Bahcall proposes a solar neutrino experiment with chlorine", "text": "John Bahcall calculated the rate at which solar neutrinos would turn chlorine into argon in a large underground tank. The rate was dominated by the rare high-energy neutrinos from ⁸B decay, and it was large enough to make the experiment practical. Raymond Davis described the detector in a companion paper in the same journal.", "categories": [ "theory" ], "luna": false, "reactions": [ "7Be-pg-8B", "8B-bp-8Be" ], "refs": [ "bahcall1964" ], "facility": null, "highlight": false }, { "id": "1968-davis-detects-solar-neutrinos-and-the", "year": 1968, "month": 5, "url": null, "title": "Davis detects solar neutrinos, and the solar neutrino problem begins", "text": "Raymond Davis and colleagues counted argon atoms produced by solar neutrinos in a large tank of chlorine-containing liquid in the Homestake mine, South Dakota. In the same issue, John Bahcall and collaborators showed that solar models predicted a rate about 2.5 times higher than Davis's limit. The gap became known as the solar neutrino problem.", "categories": [ "observation" ], "luna": false, "reactions": [ "7Be-pg-8B", "8B-bp-8Be" ], "refs": [ "davis1968", "bahcall1968" ], "facility": null, "highlight": true }, { "id": "1983-nobel-prize-for-fowler-and-chandrasekhar", "year": 1983, "month": null, "url": null, "title": "Nobel Prize for Fowler and Chandrasekhar", "text": "William Fowler shared the Nobel Prize in Physics with Subrahmanyan Chandrasekhar. Fowler's half recognized his experimental and theoretical studies of the nuclear reactions that form the chemical elements, much of it done at the Kellogg Radiation Laboratory at Caltech.", "categories": [ "experiment" ], "luna": false, "reactions": [], "refs": [ "fowler1984" ], "facility": null, "highlight": false }, { "id": "1984-radioactive-26al-is-seen-in-the", "year": 1984, "month": null, "url": null, "title": "Radioactive ²⁶Al is seen in the Galaxy", "text": "The germanium γ-ray spectrometer on the HEAO 3 satellite detected the 1809 keV line emitted when ²⁶Al decays. It was the first γ-ray line from a radioactive nucleus found in the Galaxy. The flux implied about three solar masses of ²⁶Al in the interstellar medium, all of it made within the last few million years.", "categories": [ "observation" ], "luna": false, "reactions": [ "25Mg-pg-26Al", "26Al-bp-26Mg" ], "refs": [ "mahoney1984" ], "facility": null, "highlight": false }, { "id": "1987-neutrinos-from-supernova-sn-1987a", "year": 1987, "month": null, "url": null, "title": "Neutrinos from supernova SN 1987A", "text": "A star exploded in the Large Magellanic Cloud, and the Kamiokande-II detector in Japan recorded eleven neutrino events in about 13 seconds. The IMB detector in the United States saw the burst too. It was the first detection of neutrinos from a star other than the Sun.", "categories": [ "observation" ], "luna": false, "reactions": [], "refs": [ "hirata1987" ], "facility": null, "highlight": false }, { "id": "1987-stardust-from-agb-stars-in-a", "year": 1987, "month": null, "url": null, "title": "Stardust from AGB stars in a meteorite", "text": "Grains of silicon carbide less than a micrometre across were found in the Murray meteorite, with isotopic compositions unlike anything formed in the Solar System. They condensed around red giants before the Sun was born. The heavy elements trapped in such grains carry the s-process pattern of a single star, measured atom by atom in the laboratory.", "categories": [ "observation" ], "luna": false, "reactions": [ "85Kr-ng-86Kr", "171Tm-ng-172Tm" ], "refs": [ "bernatowicz1987", "kaeppeler2011" ], "facility": null, "highlight": false }, { "id": "1989-kamiokande-ii-sees-8b-solar-neutrinos", "year": 1989, "month": null, "url": null, "title": "Kamiokande-II sees ⁸B solar neutrinos", "text": "The Kamiokande-II water detector measured high-energy solar neutrinos from the decay of ⁸B in real time. Over 450 days it found about half of the flux predicted by the standard solar model, confirming the deficit seen at Homestake with a different technique.", "categories": [ "observation" ], "luna": false, "reactions": [ "7Be-pg-8B", "8B-bp-8Be" ], "refs": [ "hirata1989" ], "facility": null, "highlight": false }, { "id": "1991-sage-the-first-gallium-experiment", "year": 1991, "month": 12, "url": null, "title": "SAGE, the first gallium experiment", "text": "The Soviet–American Gallium Experiment at Baksan used about 30 tonnes of gallium, which captures the low-energy neutrinos from proton–proton fusion. Its first result was well below the solar-model prediction.", "categories": [ "observation" ], "luna": false, "reactions": [ "1H-pp-2H" ], "refs": [ "abazov1991" ], "facility": null, "highlight": false }, { "id": "1992-gallex-observes-pp-neutrinos-at-gran", "year": 1992, "month": null, "url": null, "title": "GALLEX observes pp neutrinos at Gran Sasso", "text": "The GALLEX gallium detector at Gran Sasso measured 83 ± 19 (stat.) ± 8 (syst.) SNU. The collaboration presented this as the first observation of the neutrinos from proton–proton fusion, the reaction that starts the Sun's energy production.", "categories": [ "observation" ], "luna": false, "reactions": [ "1H-pp-2H" ], "refs": [ "gallex1992" ], "facility": null, "highlight": false }, { "id": "1994-luna-the-first-underground-accelerator", "year": 1994, "month": 10, "url": null, "title": "LUNA, the first underground accelerator", "text": "A small 50 kV accelerator was installed deep under the Gran Sasso mountain in Italy, where the rock stops most cosmic rays. It had a windowless gas target and was built to measure ³He(³He,2p)⁴He at the energies where the reaction takes place in the Sun. The facility paper describing it appeared in 1994.", "categories": [ "luna" ], "luna": true, "reactions": [ "3He-3He2p-4He" ], "refs": [ "greife1994" ], "facility": null, "highlight": true }, { "id": "1996-a-storage-ring-shows-that-bare", "year": 1996, "month": null, "url": null, "title": "A storage ring shows that bare rhenium-187 decays in years", "text": "Rhenium-187 lives about 42 billion years as a neutral atom. Fully stripped of its electrons in the GSI storage ring, it decayed with a half-life of 32.9 years, because its electron can then be created in an empty atomic orbit. Inside stars, where atoms are ionized, laboratory half-lives can therefore change completely; the result also affects the rhenium–osmium clock used to date the Galaxy.", "categories": [ "experiment" ], "luna": false, "reactions": [], "refs": [ "bosch1996" ], "facility": null, "highlight": false }, { "id": "1998-super-kamiokande-finds-neutrino-oscillations", "year": 1998, "month": null, "url": null, "title": "Super-Kamiokande finds neutrino oscillations", "text": "Super-Kamiokande found fewer muon neutrinos from the atmosphere than expected, and the deficit depended on how far the neutrinos had travelled through the Earth. The data fit neutrinos changing type, or oscillating, on the way. Oscillation requires neutrinos to have mass.", "categories": [ "observation" ], "luna": false, "reactions": [], "refs": [ "fukuda1998" ], "facility": null, "highlight": false }, { "id": "1998-solar-fusion-i", "year": 1998, "month": null, "url": null, "title": "Solar Fusion I", "text": "A group of experimentalists and theorists reviewed the nuclear reactions that produce the Sun's energy and its neutrinos. They gave recommended low-energy S-factors with uncertainties and named the experiments and calculations needed to improve them.", "categories": [ "theory" ], "luna": false, "reactions": [], "refs": [ "adelberger1998" ], "facility": null, "highlight": false }, { "id": "1999-the-nacre-compilation", "year": 1999, "month": null, "url": null, "title": "The NACRE compilation", "text": "The NACRE collaboration compiled the measured cross sections of the charged-particle reactions of stellar hydrogen, helium and carbon burning. It turned them into thermonuclear reaction rates in a common format, which stellar modellers used for many years.", "categories": [ "theory" ], "luna": false, "reactions": [], "refs": [ "angulo1999" ], "facility": null, "highlight": false }, { "id": "1999-luna-measures-3he-3he-inside-the", "year": 1999, "month": null, "url": null, "title": "LUNA measures ³He + ³He inside the solar Gamow peak", "text": "With the 50 kV accelerator, LUNA measured the fusion of two ³He nuclei down to 16.5 keV, an energy at which it occurs in the Sun. No narrow resonance was found. Such a resonance had been suggested as a nuclear explanation of the solar neutrino problem.", "categories": [ "luna" ], "luna": true, "reactions": [ "3He-3He2p-4He" ], "refs": [ "bonetti1999" ], "facility": null, "highlight": false }, { "id": "2000-a-compilation-of-stellar-neutron-capture", "year": 2000, "month": null, "url": null, "title": "A compilation of stellar neutron-capture cross sections", "text": "Bao, Beer, Käppeler, Voss, Wisshak and Rauscher surveyed the measured neutron-capture cross sections of the nuclei from hydrogen to bismuth and recommended stellar values at a thermal energy of 30 keV, with calculations where no measurement existed. It became the reference for s-process models, continued today by the KADoNiS database.", "categories": [ "experiment" ], "luna": false, "reactions": [], "refs": [ "bao2000", "dillmann2008" ], "facility": null, "highlight": false }, { "id": "2001-three-lead-stars-are-discovered", "year": 2001, "month": null, "url": null, "title": "Three lead stars are discovered", "text": "Van Eck, Goriely, Jorissen and Plez found three old, iron-poor stars more enriched in lead than in any other element heavier than iron. With fewer iron seeds for the same neutrons, the s-process in such stars runs through to lead, as the models of AGB stars had predicted.", "categories": [ "observation" ], "luna": false, "reactions": [ "209Bi-ng-210Bi", "204Tl-ng-205Tl" ], "refs": [ "vaneck2001" ], "facility": null, "highlight": false }, { "id": "2002-sno-shows-that-solar-neutrinos-change", "year": 2002, "month": null, "url": null, "title": "SNO shows that solar neutrinos change flavour", "text": "The Sudbury Neutrino Observatory in Canada used heavy water to measure both the electron neutrinos and the total number of neutrinos of all types from ⁸B decay in the Sun. The total agreed with solar models, but only about a third arrived as electron neutrinos. The solar neutrino problem was due to neutrino physics, not to the Sun.", "categories": [ "observation" ], "luna": false, "reactions": [ "8B-bp-8Be" ], "refs": [ "sno2002" ], "facility": null, "highlight": true }, { "id": "2002-nobel-prize-for-davis-and-koshiba", "year": 2002, "month": 12, "url": "https://www.nobelprize.org/prizes/physics/2002/davis/lecture/", "title": "Nobel Prize for Davis and Koshiba", "text": "Raymond Davis and Masatoshi Koshiba received the Nobel Prize in Physics for their work on neutrinos from space. Over 25 years the Homestake experiment captured about 2200 solar neutrinos, one third of the predicted number. Kamiokande confirmed the deficit and detected the neutrinos from SN 1987A.", "categories": [ "observation" ], "luna": false, "reactions": [], "refs": [ "davis2003", "hirata1987" ], "facility": null, "highlight": false }, { "id": "2003-luna-s-400-kv-accelerator-is", "year": 2003, "month": null, "url": null, "title": "LUNA's 400 kV accelerator is installed", "text": "A second, larger accelerator was installed at Gran Sasso. Its proton beam energy is known to about 300 eV, its energy spread is below 100 eV, and it drifts by only about 5 eV per hour. This stability allows the long runs needed to measure very small cross sections.", "categories": [ "luna" ], "luna": true, "reactions": [], "refs": [ "formicola2003" ], "facility": null, "highlight": false }, { "id": "2004-luna-measures-14n-p-15o-underground", "year": 2004, "month": null, "url": null, "title": "LUNA measures ¹⁴N(p,γ)¹⁵O underground", "text": "LUNA measured the slowest reaction of the CNO cycle at energies lower than surface laboratories could reach, with a solid target and a germanium detector. The extrapolated S-factor at zero energy, 1.7 ± 0.2 keV b, was lower than in earlier compilations, so the CNO cycle runs more slowly than had been assumed.", "categories": [ "luna" ], "luna": true, "reactions": [ "14N-pg-15O" ], "refs": [ "formicola2004" ], "facility": null, "highlight": false }, { "id": "2004-a-radioactive-s-process-branch-point", "year": 2004, "month": null, "url": null, "title": "A radioactive s-process branch point measured at n_TOF", "text": "At CERN's n_TOF facility the neutron-capture cross section of samarium-151, which lives about 95 years, was measured on a radioactive sample from 1 eV to 1 MeV. The stellar value turned out well above the theoretical predictions used until then.", "categories": [ "experiment" ], "luna": false, "reactions": [ "151Sm-ng-152Sm" ], "refs": [ "abbondanno2004" ], "facility": "n-tof", "highlight": false }, { "id": "2006-14n-p-15o-down-to-70", "year": 2006, "month": null, "url": null, "title": "¹⁴N(p,γ)¹⁵O down to 70 keV", "text": "With a nitrogen gas target and a large detector surrounding it, LUNA measured ¹⁴N(p,γ)¹⁵O down to 70 keV. There the cross section is only 0.24 picobarn, closer to solar energies than any earlier experiment.", "categories": [ "luna" ], "luna": true, "reactions": [ "14N-pg-15O" ], "refs": [ "lemut2006" ], "facility": null, "highlight": false }, { "id": "2007-12c-12c-fusion-measured-near-the", "year": 2007, "month": null, "url": null, "title": "¹²C + ¹²C fusion measured near the Gamow window", "text": "At the Bochum Dynamitron, Spillane and colleagues measured carbon fusion down to 2.1 MeV, using carbon targets almost free of hydrogen. They found a strong resonance at 2.14 MeV that raises the rate of one branch about fivefold near 0.8 GK, and showed how uncertain any extrapolation to lower energies is.", "categories": [ "experiment" ], "luna": false, "reactions": [ "12C-12Ca-20Ne", "12C-12Cp-23Na" ], "refs": [ "spillane2007" ], "facility": null, "highlight": false }, { "id": "2007-borexino-detects-7be-solar-neutrinos-in", "year": 2007, "month": 8, "url": null, "title": "Borexino detects ⁷Be solar neutrinos in real time", "text": "The Borexino liquid scintillator detector at Gran Sasso measured the 0.862 MeV neutrinos from ⁷Be electron capture in the Sun, one event at a time. It was the first real-time measurement of solar neutrinos below 1 MeV.", "categories": [ "observation" ], "luna": false, "reactions": [ "7Be-ec-7Li", "3He-ag-7Be" ], "refs": [ "borexino2008" ], "facility": null, "highlight": false }, { "id": "2011-solar-fusion-ii", "year": 2011, "month": null, "url": null, "title": "Solar Fusion II", "text": "A group of experimentalists and theorists reviewed the cross sections of the proton–proton chain and the CNO cycles and recommended values for solar models. The review followed an earlier one from 1998.", "categories": [ "theory" ], "luna": false, "reactions": [], "refs": [ "adelberger2011" ], "facility": null, "highlight": false }, { "id": "2014-borexino-sees-pp-neutrinos", "year": 2014, "month": 8, "url": null, "title": "Borexino sees pp neutrinos", "text": "Borexino measured the spectrum of the neutrinos from proton–proton fusion, the first reaction of the Sun's main chain. The collaboration estimated that this chain produces about 99% of the Sun's power.", "categories": [ "observation" ], "luna": false, "reactions": [ "1H-pp-2H" ], "refs": [ "borexino2014" ], "facility": null, "highlight": false }, { "id": "2015-nobel-prize-for-kajita-and-mcdonald", "year": 2015, "month": null, "url": "https://www.nobelprize.org/prizes/physics/2015/kajita/lecture/", "title": "Nobel Prize for Kajita and McDonald", "text": "Takaaki Kajita (Super-Kamiokande) and Arthur McDonald (SNO) shared the Nobel Prize in Physics for showing that neutrinos change type as they travel. This means that neutrinos have mass.", "categories": [ "observation" ], "luna": false, "reactions": [], "refs": [ "fukuda1998", "sno2002" ], "facility": null, "highlight": false }, { "id": "2017-first-beam-at-caspar", "year": 2017, "month": null, "url": "https://sanfordlab.org/news/caspar-achieves-first-beam", "title": "First beam at CASPAR", "text": "An accelerator moved from Notre Dame to the 4850 ft level of the Sanford Underground Research Facility in South Dakota delivered its first beam. It is the first underground accelerator for nuclear astrophysics in the United States, in the mine where Davis had counted solar neutrinos.", "categories": [ "facility" ], "luna": false, "reactions": [], "refs": [], "facility": null, "highlight": false }, { "id": "2017-a-review-of-12c-16o", "year": 2017, "month": null, "url": null, "title": "A review of ¹²C(α,γ)¹⁶O", "text": "deBoer and colleagues collected the measurements of ¹²C(α,γ)¹⁶O, the reaction that sets how much carbon and oxygen helium burning leaves behind, and fitted them together with an R-matrix analysis. They also followed the effect of its uncertainty on stellar models.", "categories": [ "theory" ], "luna": false, "reactions": [ "12C-ag-16O" ], "refs": [ "deboer2017" ], "facility": null, "highlight": false }, { "id": "2017-a-neutron-star-merger-makes-heavy", "year": 2017, "month": 8, "url": null, "title": "A neutron-star merger makes heavy elements", "text": "On 17 August 2017 the LIGO and Virgo detectors recorded gravitational waves from two merging neutron stars. Telescopes then found the glow of the explosion, a kilonova. Its spectra showed elements made by rapid neutron capture, the r-process.", "categories": [ "observation" ], "luna": false, "reactions": [], "refs": [ "abbott2017", "pian2017" ], "facility": null, "highlight": false }, { "id": "2018-trojan-horse-resonances-in-carbon-fusion", "year": 2018, "month": 5, "url": null, "title": "Trojan Horse resonances in carbon fusion, and a debate", "text": "Using the indirect Trojan Horse method at the LNS in Catania, Tumino and colleagues reported resonances in carbon fusion at the energies of stellar cores, raising the rate more than 25-fold near 0.5 GK. The analysis was soon challenged, and direct measurements in 2020 at Orsay and Notre Dame did not see such a rise.", "categories": [ "experiment" ], "luna": false, "reactions": [ "12C-12Ca-20Ne", "12C-12Cp-23Na" ], "refs": [ "tumino2018", "mukhamedzhanov2019", "fruet2020", "tan2020" ], "facility": null, "highlight": false }, { "id": "2019-the-felsenkeller-underground-accelerator-laboratory-opens", "year": 2019, "month": 7, "url": "https://hzdr.de/db/Cms?pNid=1029", "title": "The Felsenkeller underground accelerator laboratory opens", "text": "HZDR and TU Dresden inaugurated a 5 MV accelerator under 45 m of rock in the Felsenkeller tunnels in Dresden. The rock reduces the cosmic-ray muon flux by a factor of 40. With an active muon veto, the background is about twice that of a deep underground laboratory.", "categories": [ "facility" ], "luna": false, "reactions": [], "refs": [], "facility": null, "highlight": false }, { "id": "2020-luna-measures-deuterium-burning-for-cosmology", "year": 2020, "month": 11, "url": null, "title": "LUNA measures deuterium burning for cosmology", "text": "LUNA measured d(p,γ)³He at the energies of Big Bang nucleosynthesis with high precision. With this rate, the observed amount of primordial deuterium gives the density of ordinary matter in the Universe to 1.6%, in agreement with the cosmic microwave background.", "categories": [ "luna" ], "luna": true, "reactions": [ "2H-pg-3He" ], "refs": [ "mossa2020" ], "facility": null, "highlight": false }, { "id": "2020-borexino-detects-cno-neutrinos", "year": 2020, "month": 11, "url": null, "title": "Borexino detects CNO neutrinos", "text": "Borexino reported the first experimental evidence of neutrinos from the CNO cycle in the Sun. It shows directly that the cycle runs in stars. In the Sun it gives about one per cent of the energy.", "categories": [ "observation" ], "luna": false, "reactions": [ "14N-pg-15O", "15O-bp-15N", "13N-bp-13C" ], "refs": [ "borexino2020" ], "facility": null, "highlight": true }, { "id": "2022-a-3-5-mv-accelerator-is", "year": 2022, "month": null, "url": null, "title": "A 3.5 MV accelerator is installed under Gran Sasso", "text": "A 3.5 MV Singletron accelerator, built by High Voltage Engineering Europa, was installed underground at Gran Sasso: the MV machine of the Bellotti Ion Beam Facility (BIBF). It delivers proton, helium and carbon beams, so that helium and carbon burning can be studied underground.", "categories": [ "luna" ], "luna": true, "reactions": [ "12C-ag-16O", "13C-an-16O", "22Ne-an-25Mg" ], "refs": [ "sen2019", "junker2023" ], "facility": null, "highlight": false }, { "id": "2022-juna-measures-19f-p-20ne-underground", "year": 2022, "month": 10, "url": null, "title": "JUNA measures ¹⁹F(p,γ)²⁰Ne underground", "text": "The JUNA accelerator, under about 2400 m of rock at the China Jinping Underground Laboratory, measured ¹⁹F(p,γ)²⁰Ne down to 186 keV and found a resonance at 225 keV. Near 0.1 GK the new rate is up to 7.4 times the previous one. The reaction lets material leak out of the CNO cycle, and the faster rate may explain the calcium in one of the oldest known stars.", "categories": [ "experiment" ], "luna": false, "reactions": [ "19F-pg-20Ne" ], "refs": [ "zhang2022" ], "facility": null, "highlight": false }, { "id": "2023-the-bellotti-ion-beam-facility-is", "year": 2023, "month": 10, "url": null, "title": "The Bellotti Ion Beam Facility is inaugurated", "text": "The underground accelerator laboratory was inaugurated and named after Enrico Bellotti, the first director of the Gran Sasso laboratory, who started underground accelerator physics there. It runs as a user facility, with beam time given through yearly calls.", "categories": [ "luna" ], "luna": true, "reactions": [], "refs": [ "junker2023" ], "facility": null, "highlight": false }, { "id": "2024-the-stellar-decay-of-thallium-205", "year": 2024, "month": 11, "url": null, "title": "The stellar decay of thallium-205 is measured", "text": "Bare thallium-205 ions circulating in the GSI storage ring were seen to decay into lead-205 by bound-state β decay, with a half-life of 291 days. In stars this decay makes lead-205, a radioactive nucleus whose traces in meteorites help date the birth of the Sun; the long-sought measurement fixes a key nuclear input of that clock.", "categories": [ "experiment" ], "luna": false, "reactions": [], "refs": [ "leckenby2024" ], "facility": null, "highlight": false }, { "id": "2025-solar-fusion-iii", "year": 2025, "month": null, "url": null, "title": "Solar Fusion III", "text": "A new review collected the data and theory for hydrogen burning in the Sun and other stars that appeared after Solar Fusion II. It gives recommended S-factors with uncertainties for the proton–proton chain and the CNO cycles.", "categories": [ "theory" ], "luna": false, "reactions": [], "refs": [ "acharya2025" ], "facility": null, "highlight": false }, { "id": "2026-neutron-capture-on-radioactive-niobium-94", "year": 2026, "month": 8, "url": null, "title": "Neutron capture on radioactive niobium-94 is measured", "text": "Stardust grains older than the Sun hold more molybdenum-94 than earlier models predicted. Its production depends on niobium-94, a radioactive branch point of the s-process, where neutron capture competes with decay. At CERN's n_TOF its capture cross section was measured for the first time. The result confirms the general scale of the theoretical estimates; used in fully coupled models of low-mass giant stars, together with their improved physics, it brings them into agreement with the grains.", "categories": [ "experiment" ], "luna": false, "reactions": [], "refs": [ "balibreacorrea2026" ], "facility": "n-tof", "highlight": false } ] }