¹⁷O(p,α)¹⁴N · Reaction atlas

Oxygen-17 captures a proton and splits into nitrogen-14 and a helium nucleus. This closes the second CNO cycle and destroys oxygen-17.

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.

Facts

How well known: 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.
Live evaluation: No live evaluation yet · Evaluations
Reaction rates: Explore the rates →
Q-value · energy released: 1.192 MeV
Gamow window: 51 ± 14 keVcore of a 15 M☉ star, 35 MK (CNO-II)
Kind: Particle-exchange reaction

How it was measured

6 measurements, 2005–2016, 2 at LUNAShow the list

2005
CSNSM, OrsayCentre de Sciences Nucléaires et de Sciences de la Matière (CNRS/IN2P3 and Université Paris-Sud), since 2020 part of IJCLab
Direct measurement at the surface · around Ep = 194 keV
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. [1]
2007
Holifield Radioactive Ion Beam Facility, Oak Ridge
Inverse kinematics and recoil separators · 183 keV resonance
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. [2]
2010
Trojan Horse method · 0–300 keV
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. [3]
2015
LUNA 400 kVLaboratori Nazionali del Gran Sasso (INFN)
Direct measurement underground · Ep = 194.8 keV resonance
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. [4]
2015
Trojan Horse method · 65 and 183 keV resonances
Improved Trojan-Horse analysis of narrow-resonance strengths; the 65 keV strength was used to renormalize the same resonance in the (p,γ) channel. [5]
2016
LUNA 400 kVLaboratori Nazionali del Gran Sasso (INFN)
Direct measurement underground · 64.5 keV resonance
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. [6]

Measurements (EXFOR)

Every dataset EXFOR holds for this reaction, drawn by the energies it covers, against the energies a star uses.

17 datasets in 9 EXFOR entries, 1962–2016 · 7 without an energy range, not drawn

core of a 15 M☉ star, T₉ = 0.035 (35 MK)

Lowest energy in EXFOR: 64.5 keV; Bruno et al., 2016 · ωγ · O2313.002
Distance from the Gamow peak: Only the upper edge of the window; E₀ = 51.4 keV, window 37–65.7 keV
Rate from energies not in EXFOR: > 99.99%; at T₉ = 0.035, smooth estimate · 85% of it lies below the lowest energy in EXFOR

1 resonance-strength datasets reach into this window: the smooth estimate does not count resonances.

Gamow window, hatched where no measurement reaches
Outlined bars are shown but not counted (the rule is under “How these numbers are made”).
A diamond is a dataset at a single energy. Bars running off the right edge continue to higher energies.

The datasets of the gap map, by quantity

The datasets of the gap map, by quantity
Quantity	Datasets	E_cm range (keV)
dσ/dΩangular distribution	5	183 keV – 494 MeV
Yyield	1	183 keV – 190 keV
ωγresonance strength	3	64.5 keV – 184 keV
…other	1	183 keV – 183 keV

How these numbers are made

Lowest measured energy, everywhere in the data explorer: the lowest centre-of-mass energy at which a dataset in EXFOR measures the reaction itself (cross section, S-factor, angular distribution, yield or resonance strength), judged point by point. A point counts when it is a value, not an upper or lower limit, when it lies at least one standard deviation above zero, and when its energy is physical: at least 1 keV for charged particles, and not below the threshold of an endothermic reaction. Not counted: extrapolated, calculated, evaluated or derived values; superseded, deleted or preliminary data; ratios; a single S-factor value, which in EXFOR is a fit result; and indirect methods (Trojan horse, Coulomb dissociation, ANC, surrogate reactions), recognized from EXFOR's method and analysis codes, their text and the title. Frame and unit errors of EXFOR are corrected first, and values the literature shows to be upper limits are read as limits, from a list that gives the evidence for each. Datasets that reach the same energy within 0.5% are all credited, earliest first. Rate from energies not in EXFOR: the share of the rate integrand at that temperature outside the energy ranges the counted datasets cover (from their lowest measured point to their highest), with a constant S-factor (σ ∝ S(E₀)/E · e^−2πη, so the integrand is e^(−E/kT − 2πη)); for a neutron capture, σ ∝ 1/v. Resonances make the real integrand lumpy, so read it as a smooth baseline.

All measurements (17)Compound nucleus ¹⁸F

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.

Peak energy E₀ ± half the 1/e width, centre of mass, from the AME2020 masses.

Evaluations

Compilations that combine the data into a recommended rate.

—E. G. Adelberger et al., Rev. Mod. Phys. 83, 195 (2011) [7]
—B. Acharya et al., Rev. Mod. Phys. 97, 035002 (2025) [8]

Open questions

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.

Related reactions

References

1.
A. Chafa, V. Tatischeff et al.
Hydrogen burning of ¹⁷O in classical novae
Phys. Rev. Lett. 95, 031101 (2005) · 10.1103/PhysRevLett.95.031101 · arXiv:astro-ph/0506500
2.
B. H. Moazen et al.
Measurement of the 183 keV resonance in ¹⁷O(p,α)¹⁴N using a novel technique
Phys. Rev. C 75, 065801 (2007) · 10.1103/PhysRevC.75.065801
3.
M. L. Sergi, C. Spitaleri, M. La Cognata et al.
New high accuracy measurement of the ¹⁷O(p,α)¹⁴N reaction rate at astrophysical temperatures
Phys. Rev. C 82, 032801(R) (2010) · 10.1103/PhysRevC.82.032801
4.
C. G. Bruno et al. (LUNA Collaboration)
Resonance strengths in the ¹⁷,¹⁸O(p,α)¹⁴,¹⁵N reactions and background suppression underground
Eur. Phys. J. A 51, 94 (2015) · 10.1140/epja/i2015-15094-yLUNA
5.
M. L. Sergi, C. Spitaleri, M. La Cognata et al.
Improvement of the high-accuracy ¹⁷O(p,α)¹⁴N reaction-rate measurement via the Trojan Horse method for application to ¹⁷O nucleosynthesis
Phys. Rev. C 91, 065803 (2015) · 10.1103/PhysRevC.91.065803
6.
C. G. Bruno et al. (LUNA Collaboration)
Improved direct measurement of the 64.5 keV resonance strength in the ¹⁷O(p,α)¹⁴N reaction at LUNA
Phys. Rev. Lett. 117, 142502 (2016) · 10.1103/PhysRevLett.117.142502 · arXiv:1610.00483LUNA
7.
E. G. Adelberger et al.
Solar fusion cross sections II: the pp chain and CNO cycles
Rev. Mod. Phys. 83, 195 (2011) · 10.1103/RevModPhys.83.195
8.
B. Acharya et al.
Solar fusion III: New data and theory for hydrogen-burning stars
Rev. Mod. Phys. 97, 035002 (2025) · 10.1103/8lm7-gs18 · arXiv:2405.06470
9.
D. Rapagnani et al. (LUNA Collaboration)
Revision of the CNO cycle: rate of ¹⁷O destruction in stars
Phys. Rev. C 111, 025805 (2025) · 10.1103/PhysRevC.111.025805LUNA

How to cite this page

J. Skowronski, ¹⁷O(p,α)¹⁴N, in Reaction atlas, 2026-10-12, https://jskowron.eu/atlas/17O-pa-14N.

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