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arXiv 2404.01271nucl-ex
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$^{15}$N($α,γ$)$^{19}$F 中 $E_{\rm{c.m.}} = 1323$ 和 $1487$ keV 共振的能量、强度与 α 宽度测量

Energy, strength, and alpha width measurements of $E_{\rm{c.m.}} = 1323$ and $1487$ keV resonances in $^{15}$N($α,γ$)$^{19}$F

R. Fang, J. Görres, R. J. deBoer, S. Moylan, A. Sanchez, T. L. Bailey, S. Carmichael, J. Koros, K. Lee, K. Manukyan, M. Matney, J. P. McDonaugh, D. Robertson, J… 展开作者

R. Fang, J. Görres, R. J. deBoer, S. Moylan, A. Sanchez, T. L. Bailey, S. Carmichael, J. Koros, K. Lee, K. Manukyan, M. Matney, J. P. McDonaugh, D. Robertson, J. Rufino, E. Stech, M. Couder

备注：
12 pages, 7 figures, 3 tables. Manuscript submitted to Phys. Rev. C on March 21, 2024
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AI总结：

本文重新测量了 $^{15}$N($α,γ$)$^{19}$F 反应中两个关键共振的能量、强度和 α 宽度，修正了较高共振能量并建议采用更大的 α 宽度，使低质量 AGB 恒星相关温度下的反应率增加约 15%。

摘要：

$^{15}$N($α,γ$)$^{19}$F 反应在渐近巨星支（AGB）恒星中产生 $^{19}$F，其中位于 $E_{\rm{c.m.}} = 1323 \pm 2$ 和 $1487 \pm 1.7$ keV 的两个共振的低能尾部估计对这些环境中总反应率的贡献约为 $30\\%$。然而，最近的测量在这两个共振的能量、强度以及相应的 α 宽度方面显示出分歧，导致外推到氦燃烧能量下的截面的系统不确定度增大。基于这一动机，我们在圣母大学核科学实验室对 $^{15}$N$(α,γ)^{19}$F 进行了新的测量。实验装置由 α 粒子束轰击固体 Ti$^{15}$N 靶组成，γ 射线谱学使用高纯锗探测器完成。利用多普勒修正后的 γ 射线能量，我们确认较低的共振能量为 $1321.6 \pm 0.6$ keV，并得到较高共振的能量为 $1479.4 \pm 0.6$ keV，该值与先前弹性散射研究得到的结果更为一致。我们发现两个共振的共振强度与文献中的大多数数值一致，但建议对 $E_{\rm{c.m.}} = 1487$ keV 共振采用更大的 α 宽度。更大的 α 宽度意味着在与低质量 AGB 恒星相关的温度 $T < 0.1$ GK 下，反应率增加约 $15\\%$。反应率增加的影响需要进一步研究。

英文摘要：

The $^{15}$N($α,γ$)$^{19}$F reaction produces $^{19}$F in asymptotic giant branch (AGB) stars, where the low energy tails of two resonances at $E_{\rm{c.m.}} = 1323 \pm 2$ and $1487 \pm 1.7$ keV are estimated to contribute about $30\%$ of the total reaction rate in these environments. However, recent measurements have shown discrepancies in the energies, the strengths, and the corresponding alpha widths of these two resonances, resulting in an increase in the systematic uncertainty of the extrapolated cross section to helium burning energies. With this motivation, we have undertaken new measurements of the $^{15}$N$(α,γ)^{19}$F at the University of Notre Dame Nuclear Science Laboratory. The setup consisted of an alpha particle beam impinged on a solid Ti$^{15}$N target with gamma-ray spectroscopy accomplished using a high purity germanium detector. Using the Doppler corrected gamma-ray energies, we confirmed the lower resonance energy to be $1321.6 \pm 0.6$ keV and found a value for the higher one of $1479.4 \pm 0.6$ keV that is more consistent with those found from previous elastic scattering studies. We found that the resonance strengths for both were consistent with most values found in the literature, but a larger alpha width has been recommended for the $E_{\rm{c.m.}} = 1487$ keV resonance. The larger alpha width suggests a reaction rate increase of about $15\%$ at temperatures $T < 0.1$ GK relevant to low mass AGB stars. The impact of the increased reaction rate requires further investigations.

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