基于n_TOF和GELINA测量的中子俘获与透射实验获得的改进型⁹⁴Mo中子共振参数
Improved $^{94}$Mo neutron resonance parameters from neutron capture and transmission measurements at n_TOF and GELINA
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中文总结 AI 辅助
本研究通过n_TOF和GELINA的中子实验联合R矩阵分析得到改进的⁹⁴Mo中子共振参数，发现其s过程麦克斯韦平均截面降低25%，但对AGB恒星⁹⁴Mo产额影响仅3%-4%，厘清了相关核不确定性与分支流效应的关系。
中文摘要 AI 辅助
我们报告了在欧洲核子中心（CERN）的n_TOF装置上完成的、中子能量从几eV到约250 keV的⁹⁴Mo(n,γ)⁹⁵Mo截面的高分辨率测量，以及在欧盟委员会联合研究中心（JRC）海尔赫特的GELINA装置上完成的、中子能量到32 keV的⁹⁴Mo(n,tot)截面测量。对俘获和透射数据的联合R矩阵分析得到了显著改进的⁹⁴Mo中子共振参数。本次分析共观测到186个共振，其中127个为本研究首次报道。在与慢中子俘获过程（s过程）相关的恒星温度下，由此得到的麦克斯韦平均截面比之前的评价和文献值低约25%。为评估修正后截面的天体物理影响，我们对低质量渐近巨星分支（AGB）恒星进行了s过程核合成计算。尽管⁹⁴Mo(n,γ)⁹⁵Mo反应速率大幅降低，最终核素产额仅变化3%-4%。这表明AGB恒星中⁹⁴Mo的同位素收支主要由⁹⁴Nb处的分支流控制，而非⁹⁴Mo自身的中子俘获破坏。因此，新截面有助于厘清s过程中⁹⁴Mo产生的核截面不确定性与分支流效应之间的关联。
英文摘要
We report high-resolution measurements of the $^{94}\mathrm{Mo}(\mathrm{n},γ)^{95}\mathrm{Mo}$ cross section in the neutron energy range from a few eV up to about 250 keV, performed at the n_TOF facility (CERN), and of the $^{94}\mathrm{Mo}(\mathrm{n},\mathrm{tot})$ cross section up to 32 keV, measured at GELINA (JRC Geel). A combined R-matrix analysis of capture and transmission data yields significantly improved neutron-resonance parameters for $^{94}$Mo. A total of 186 resonances were observed in this analysis of which 127 reported here for the first time. The resulting Maxwellian-averaged cross section at stellar temperatures relevant to the slow neutron-capture process (s-process) is approximately 25% lower than previous evaluations and literature values. To assess the astrophysical impact of the revised cross section, we performed s-process nucleosynthesis calculations for low-mass asymptotic giant branch stars. Despite the substantial reduction in the $^{94}\mathrm{Mo}(\mathrm{n},γ)^{95}\mathrm{Mo}$ rate, the final yields vary by only 3-4%. This demonstrates that the isotopic budget of $^{94}$Mo in AGB stars is primarily governed by the branching flow at $^{94}\mathrm{Nb}$ rather than by the neutron-capture destruction on $^{94}$Mo itself. The new cross section thus helps disentangle nuclear cross-section uncertainties from branching-flow effects in the s-process production of $^{94}$Mo.
