Abstract

Electron captures on nuclei play an essential role in the dynamics of the collapsing core of a massive star that leads to a supernova explosion. We propose a novel thermodynamically consistent approach to calculate capture rates and cross sections of \({{e}^{ - }}\) capture on hot nuclei in the stellar interior. The method is based on the quasi-particle random phase approximation extended to finite temperature using the tool of the superoperator formalism. By the example of \(^{{54,56}}\)Fe it is shown that thermodynamically consistent incorporation of thermal effects leads to a stronger temperature dependence of the \({{e}^{ - }}\)-capture rates and cross sections for iron group nuclei than predicted by the shell-model calculations. The combined action of thermal effects and pairing correlations on the unblocking of Gamow–Teller \(p \to n\)-transitions is considered for neutron-rich nuclei around N = 50. It is shown that it is thermal effects that lead to the unblocking of low-energy transitions. Due to this, as well as to the contribution of forbidden transitions, the electron capture does not stop at nuclei with N = 50.

中文翻译：

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热核理论和天体物理应用的超级算子方法：II—恒星中的电子捕获

摘要

原子核上的电子捕获在导致超新星爆炸的大质量恒星坍缩核心的动力学中起着至关重要的作用。我们提出了一种新的热力学一致方法来计算在恒星内部的热核上捕获的\({{e}^{ - }}\)捕获率和横截面。该方法基于使用超级算子形式工具将准粒子随机相位近似扩展到有限温度。以\(^{{54,56}}\) Fe 为例，表明热效应的热力学一致结合导致\({​​{e}^{ - }}\)的温度依赖性更强-铁族核的捕获率和横截面比壳模型计算预测的要高。对于N = 50附近的富中子核，考虑了热效应和配对相关性对 Gamow-Teller \(p \to n\)跃迁的解除阻塞的联合作用。结果表明，是热效应导致解除低能量跃迁的阻碍。由于这一点，以及禁止跃迁的贡献，电子捕获不会在N = 50 的原子核处停止。