This project aims to investigate the most important weak interaction nuclei in the presupernova evolution of massive stars. To achieve this goal, an ensemble containing 728 nuclei in the mass range of A = 1–100 was considered. We computed the mass fractions of these nuclei using Saha’s equation for predetermined values of T, ρ, and Y _e and assuming nuclear statistical equilibrium. The nuclear partition functions were obtained using a newly introduced recipe where excited states, up to 10 MeV, were treated as discrete. The weak interaction rates (electron capture (ec) and β-decay (bd)) were calculated in a totally microscopic fashion using the proton–neutron quasiparticle random phase approximation model and without assuming the Brink–Axel hypothesis. The calculated rates were coupled with the computed mass fractions to investigate the time rate of change of lepton to baryon fraction of the stellar matter. We compare our results with the previous calculations reported in the literature. Noticeable differences up to orders of magnitude are reported with previous calculations. These differences may influence the evolution of the star in the later stages of presupernova. We present a list of the top 50 ec and bd nuclei, which have the largest effect on Y _e for conditions after silicon core burning. The competition between the ec and bd rates in the stellar core was investigated and it was found that Y _e = 0.424–0.455 is the interval where the bd results are bigger than the ec rates.

该项目旨在研究大质量恒星前超新星演化中最重要的弱相互作用核。为了实现这个目标，我们考虑了一个包含 728 个原子核的集合，质量范围为A = 1-100。对于T、ρ和Y _{e 的}预定值，并假设核统计平衡，我们使用萨哈方程计算了这些核的质量分数。核分配函数是使用新引入的配方获得的，其中高达 10 MeV 的激发态被视为离散的。弱相互作用率（电子俘获 (ec) 和β -decay (bd)) 使用质子-中子准粒子随机相位近似模型以完全微观的方式计算，并且不假设 Brink-Axel 假设。计算出的速率与计算出的质量分数相结合，以研究轻子到恒星物质重子分数的时间变化率。我们将我们的结果与文献中报道的先前计算进行比较。先前的计算报告了高达数量级的显着差异。这些差异可能会影响前超新星后期阶段恒星的演化。我们列出了对Y _e影响最大的前 50 个 ec 和 bd 核 用于硅芯燃烧后的条件。研究了恒星核心中 ec 和 bd 速率之间的竞争，发现Y _e = 0.424-0.455 是 bd 结果大于 ec 速率的区间。