Gamow-Teller strength distributions at finite temperatures and electron capture in stellar environments

TL;DR

This paper introduces a novel method using Thermo-Field-Dynamics to compute stellar weak-interaction rates, revealing how finite temperatures influence Gamow-Teller distributions and electron capture processes in nuclei relevant to stellar environments.

Contribution

It presents a new approach for calculating nuclear weak-interaction responses at finite temperatures, including the effects on Gamow-Teller distributions and electron capture rates in stellar conditions.

Findings

Thermal effects lower the GT+ centroid energy.

Negative and low-energy transitions become possible at higher temperatures.

Unblocking of GT+ transitions in neutron-rich nuclei is temperature-sensitive.

Abstract

We propose a new method to calculate stellar weak-interaction rates. It is based on the Thermo-Field-Dynamics formalism and allows the calculation of the weak-interaction response of nuclei at finite temperatures. The thermal evolution of the GT$_+$ distributions is presented for the sample nuclei $^{54, 56}$Fe and ~$^{76,78,80}$Ge. For Ge we also calculate the strength distribution of first-forbidden transitions. We show that thermal effects shift the GT$_+$ centroid to lower excitation energies and make possible negative- and low-energy transitions. In our model we demonstrate that the unblocking effect for GT$_+$ transitions in neutron-rich nuclei is sensitive to increasing temperature. The results are used to calculate electron capture rates and are compared to those obtained from the shell model.