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arXiv 1910.09360nucl-ex
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在CERN n_TOF装置上测量高达300~ keV的$^{70}$ Ge($n,γ$)截面

Measurement of the $^{70}$Ge($n,γ$) cross section up to 300~keV at the CERN n_TOF facility

A. Gawlik, C. Lederer-Woods, the n_TOF collaboration

摘要:

中等质量核的中子俘获数据对于大质量恒星中慢中子俘获过程的弱分量中的核合成至关重要。在欧洲核子研究中心(CERN)的中子飞行时间装置n_TOF上测量了$s$ ~过程中产生的$^{70}$ Ge的($n,γ$)截面。共振俘获核的能量可达40 keV,平均截面可达300 keV。恒星的横截面是从$kT=5$ ~keV到$kT=100$ keV计算的,与Walter和Beer(1985)以前的测量以及最近的评估非常一致。在所涵盖的大部分中子能量范围内,平均截面与Walter和Beer(1985)一致,而在150 keV以上的中子能量范围内,平均截面系统地较小。我们已经计算了同位素丰度产生的$s$过程的环境中,在25太阳质量的恒星的两个初始金属丰度(低于太阳,接近太阳)。虽然低金属丰度模型最好地再现了太阳系锗同位素丰度,但接近太阳的模型显示出与质量数A=60-80之间的太阳系丰度良好的全球匹配。

英文摘要:

Neutron capture data on intermediate mass nuclei are of key importance to nucleosynthesis in the weak component of the slow neutron capture processes, which occurs in massive stars. The ($n,γ$) cross section on $^{70}$Ge, which is mainly produced in the $s$~process, was measured at the neutron time-of-flight facility n_TOF at CERN. Resonance capture kernels were determined up to 40~keV neutron energy, and average cross sections up to 300~keV. Stellar cross sections were calculated from $kT=5$~keV to $kT=100$ keV and are in very good agreement with a previous measurement by Walter and Beer (1985), and recent evaluations. Average cross sections are in agreement with Walter and Beer (1985) over most of the neutron energy range covered, while being systematically smaller for neutron energies above 150~keV. We have calculated isotopic abundances produced in $s$-process environments in a 25 solar mass star for two initial metallicities (below solar, and close to solar). While the low metallicity model reproduces best the solar system germanium isotopic abundances the close to solar model shows a good global match to solar system abundances between mass numbers A=60-80.

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