AI 中文总结
研究\(^{8}\)Li(n,\(\gamma\))\(^{9}\)Li 反应，在 R 矩阵框架内评估其截面和反应速率，考虑非共振直接俘获与共振俘获，用蒙特卡罗抽样处理参数不确定性，得到俘获率，结果与前人上限一致，优于此前理论预测。
AI 中文摘要
\(^{8}\)Li(n,\(\gamma\))\(^{9}\)Li 反应在非均匀大爆炸核合成模型以及 r 过程核合成情景中，对于合成 A = 8 稳定间隙以外的原子核具有重要意义。然而，由于\(^{8}\)Li 半衰期短且缺乏中子靶，无法直接测量该反应。因此，基于间接实验方法和理论计算的现有反应速率估计相差几个数量级。在本工作中，在唯象 R 矩阵框架内评估\(^{8}\)Li(n,\(\gamma\))\(^{9}\)Li 中子俘获截面和相应的热核反应速率，包括非共振直接俘获（DC）和通过\(E_{x}=4.30\) MeV 的\(5/2^{-}\)态的共振俘获。利用蒙特卡罗抽样传播与 R 矩阵输入参数相关的不确定性，而对通道半径的敏感性作为 R 矩阵模型不确定性处理。通过将这两个不确定性贡献正交相加，得到计算截面和反应速率中的有效总不确定性。在 T = 1 GK 时，总俘获率为\(983.9^{+410.9}_{-261.5}~cm^{3}\,mol^{-1}\,s^{-1}\)，低温（T = 0.01 - 0.4 GK）时 DC 占主导，高温（T = 0.5 - 5 GK）时\(5/2^{-}\)共振占主导。本结果与 Kobayashi 等人的上限一致，而之前的理论预测超出该上限 3 - 50 倍。
英文摘要
The $^{8}$Li$(n,γ)^{9}$Li reaction is considered significant for the synthesis of nuclei beyond the $A=8$ stability gap in inhomogeneous big-bang nucleosynthesis models, as well as in $r$-process nucleosynthesis scenarios. However, direct measurement of this reaction is precluded by the short half-life of $^{8}$Li and the absence of a neutron target. Consequently, existing reaction rate estimates based on indirect experimental methods and theoretical calculations differ by orders of magnitude. In the present work, the $^{8}$Li(n,$γ$)$^{9}$Li neutron-capture cross section and the corresponding thermonuclear reaction rate are evaluated within a phenomenological $R$-matrix framework, including both non-resonant direct capture (DC) and resonant capture through the $5/2^{-}$ state at $E_{x} = 4.30$~MeV. The uncertainties associated with the $R$-matrix input parameters are propagated using Monte Carlo sampling, while the sensitivity to the channel radius is treated as an $R$-matrix model uncertainty. The effective total uncertainties in the calculated cross sections and reaction rates are obtained by adding these two uncertainty contributions in quadrature. We obtain a total capture rate of $983.9^{+410.9}_{-261.5}~\mathrm{cm^{3}\,mol^{-1}\,s^{-1}}$ at $T = 1$~GK, with DC dominating at low temperatures ($T=0.01-0.4$~GK) and the $5/2^{-}$ resonance at higher temperatures ($T=0.5-5$~GK). The present results are consistent with the upper limit of Kobayashi et al.~\cite{Kobayashi2003}, which previous theoretical predictions exceed by factors of 3-50.
Comments11 Pages, 7 figures
