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.
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.
Facts
- How well known
- Measured once, on a tiny radioactive sample, to about 14%; its neighbouring branch points are known only from calculations.
- Live evaluation
- No live evaluation yet · Evaluations
- Reaction rates
- Explore the rates →
- Q-value · energy released
- 5.895 MeV
- Half-life of 147Pm
- 2.62 yr
- Measured in the laboratory; in a star, thermally excited states and ionization can change it. It decides how often this nucleus decays before it captures a neutron.
- Thermal energy kT
- about 8–23 keV, the energy of a gas at 90–270 million kelvin
By stellar site
- 7.8 keVAGB 13C pocket, 90 MK
- 23 keVAGB thermal pulse, 0.27 GK
- Why no Gamow window
- A neutron feels no Coulomb barrier, so there is no Gamow window: the relevant energies are those of the thermal distribution itself, around kT.
- Product 148Pm
- radioactive, t½ = 5.37 d
- Kind
- Radiative capture
How it was measured
1 measurement, 2003Show the listHide the list
2003
Karlsruhe Van de GraaffKernforschungszentrum Karlsruhe (now Karlsruhe Institute of Technology)
Activation · quasi-Maxwellian neutron spectrum
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. [1]
Measurements (EXFOR)
Every dataset EXFOR holds for this reaction, drawn by the energies it covers, against the energies a star uses.
69 datasets in 18 EXFOR entries, 1947–2019 · 30 without an energy range, not drawn
- Lowest energy in EXFOR
- 24.8 meV
- Gorshkov et al., 1957 · σ · 40363.003
- Maxwellian averages measured
- 29 sets
- kT from 5 keV to 100 keV
- Rate from energies not in EXFOR
- 100%
- at kT = 7.76 keV, smooth estimate
- Energies that matter at kT = 7.76 keV
- 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
| Quantity | Datasets | E_cm range (keV) |
|---|---|---|
| σcross section | 4 | 24.8 meV – 25.1 meV |
| ωγresonance strength | 1 | 5.32 eV – 6.87 eV |
| MACSMaxwellian average | 29 | 5 keV – 100 keV |
| …other | 5 | 25.1 meV – 755 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.
Details
How well known, in detail: One activation measurement, on a 28 ng sample, known to about 14%; the neighbouring branch points 147Nd and 148Pm rest on calculations.
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).
Evaluations
Compilations that combine the data into a recommended rate.
Related reactions
References
- 1.
R. Reifarth et al.
Stellar neutron capture on promethium: implications for the s-process neutron density
Astrophys. J. 582, 1251 (2003)
- 2.
Z. Y. Bao, H. Beer, F. Käppeler, F. Voss, K. Wisshak, T. Rauscher
Neutron cross sections for nucleosynthesis studies
At. Data Nucl. Data Tables 76, 70 (2000) · 10.1006/adnd.2000.0838
- 3.
I. Dillmann et al.
Proc. Int. Conf. on Nuclear Data for Science and Technology 2007 (EDP Sciences, 2008), p. 575 (2008) · 10.1051/ndata:07303 · arXiv:0806.2076
- 4.
F. Käppeler, R. Gallino, S. Bisterzo, W. Aoki
The s process: nuclear physics, stellar models, and observations
Rev. Mod. Phys. 83, 157 (2011) · 10.1103/RevModPhys.83.157 · arXiv:1012.5218
How to cite this page
J. Skowronski, 147Pm(n,γ)148Pm, in Reaction atlas, 2026-10-12, https://jskowron.eu/atlas/147Pm-ng-148Pm.
Cite the date you used; it is the last change to this page.
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