Measurement of theErc.m.=259 keV resonance in theN

Abstract

The14 N(p, γ) 15 O reaction regulates the power generated by the CN cycle and thus impacts the structure and evolution of every star at some point in its life. The lowest positive-energy resonance in this reaction is located at E c.m. r = 259 keV, too high in energy to strongly influence quiescent stellar burning. However, the strength of this resonance is used as a cross-section normalization for lower-energy measurements of this reaction. We report on new measurements of the energy, strength and γ-ray branching ratios for the 259-keV resonance, using different detection and dataanalysis schemes. We have also re-evaluated previous results, where possible. Our new recommended strength of ωγ = 12.6(3) meV is in agreement with the previous value of 13.1(6) meV, but is more precise and thus provides a more reliable normalization for low-energy (p,γ) measurements.

Resonance strengths in the N14 ( p,γ)O15Gyürky1, Halász2, Kiss3 et al. 2019Phys. Rev. C140110View full textAdd to dashboardCite

“…If we take into account the total uncertainties, the new result for the E p = 278 keV resonance strength is in good agreement with the adopted values recommended by the Solar Fusion II compilation [5] as well as by the more recent work of Daigle et al [6] (see Table I). We do not quote here a new recommended value; we just note that considering our new value determined with an independent technique, the strength recommended by the Solar Fusion II compilation [5] and especially its somewhat higher uncertainty seems more appropriate than the value of Daigle et al [6] with its very small error bar. The results of those experiments where the E p = 278 keV resonance is used as a normalization point do not change by the present result.…”

“…[5] but its uncertainty is reduced to 2.4%. This uncertainty seems surprisingly low considering on one hand the stopping power uncertainty which is common to almost all the experiments and on the other hand the difficulty in characterizing the implanted targets used by Daigle et al [6].…”

“…Based on several measurements, the recommended value of the strength has an uncertainty of 4.6%, as given by the latest compilation of solar fusion reactions [5]. In the paper of Daigle et al [6] published after the above cited compilation, a new result was presented and the literature data were also critically re-analyzed. Their recommended value is in agreement with that of Ref.…”

“…At low energies the 14 N(p, γ ) 15 O reaction proceeds mostly through the direct capture mechanism with contribution from Woodbury et al [9] 1949 activation 10 Duncan and Perry [10] 1951 activation 20 Bashkin et al [11] 1955 prompt γ 13 ± 3 Hebbard et al [12] 1963 prompt γ 14 ± 2 Becker et al [13] 1982 prompt γ 14 ± 1 Runkle et al [14] 2005 prompt γ 13.5 ± 1.2 Imbriani et al [15] 2005 prompt γ 12.9 ± 0.9 Bemmerer et al [16] 2006 prompt γ 12.8 ± 0.6 Daigle et al [6] 2016 prompt γ 12.6 ± 0.6…”

Astrophysical S factor of the N14(p,γ)O15

“…Its S-factor curve is essentially flat over a wide energy range [18], indicating a dominance of direct capture and capture through very wide resonances. Indeed, the 6.79 MeV transition plays only a secondary role for the low-energy resonance at E = 259 keV [27,28], which has recently emerged as a precise normalization point [17,25,26,33,34]. The transition has not even been detected in the subsequent resonance at E = 987 keV [35].…”