用增广核质量模型重新检验r过程核合成的温度和中子密度条件
Reexamining the temperature and neutron density conditions for r-process nucleosynthesis with augmented nuclear mass models
摘要：
我们探索的影响，核质量的r-过程核合成所需的温度和中子密度的条件下，使用四个核质量模型增强了最新的原子质量评估。对于每一个模型，我们推导出的条件下观察到的丰度峰在质量数A ~ 80，130，和195的等待点近似下，并进一步确定的条件，可以最好地再现的r-过程丰度模式（r-模式）推断的太阳系和银河系晕中的贫金属恒星观察。我们发现：（1）在A ~ 80和195处产生丰度峰的条件有很大的不同，这表明，至少对某些核质量模型来说，这两个峰不是同时产生的;（2）N = 126闭合中子壳层临界等待点（CWP）核所需的典型条件与N = 126闭合中子壳层临界等待点（CWP）核所需的典型条件有明显的重叠。（3）N = 82的CWP核所需的典型条件可以重现在贫金属星HD 122563上观测到的r-斑图，这与太阳的r-斑图有很大的不同。我们还研究了核质量的不确定性如何影响r-过程所需的条件，并确定了一些关键的核，包括76镍到78镍，82锌，131镉，和132镉在稀有同位素束设施的精确质量测量。
英文摘要：
We explore the effects of nuclear masses on the temperature and neutron density conditions required for r-process nucleosynthesis using four nuclear mass models augmented by the latest atomic mass evaluation. For each model we derive the conditions for producing the observed abundance peaks at mass numbers A ~ 80, 130, and 195 under the waiting-point approximation and further determine the sets of conditions that can best reproduce the r-process abundance patterns (r-patterns) inferred for the solar system and observed in metal-poor stars of the Milky Way halo. In broad agreement with previous studies, we find that (1) the conditions for producing abundance peaks at A ~ 80 and 195 tend to be very different, which suggests that, at least for some nuclear mass models, these two peaks are not produced simultaneously; (2) the typical conditions required by the critical waiting-point (CWP) nuclei with the N = 126 closed neutron shell overlap significantly with those required by the N=82 CWP nuclei, which enables coproduction of abundance peaks at A ~ 130 and 195 in accordance with observations of many metal-poor stars; and (3) the typical conditions required by the N = 82 CWP nuclei can reproduce the r-pattern observed in the metal-poor star HD 122563, which differs greatly from the solar r-pattern. We also examine how nuclear mass uncertainties affect the conditions required for the r-process and identify some key nuclei including76Ni to 78Ni, 82Zn, 131Cd, and 132Cd for precise mass measurements at rare-isotope beam facilities.
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