Investigation of weak-rates for odd-A nuclei for presupernova simulations

TL;DR

This paper calculates weak decay rates for odd-A nuclei under stellar conditions using a deformed pn QRPA model, emphasizing the importance of nuclear deformation and providing results that align with shell model calculations.

Contribution

It introduces a state-by-state microscopic calculation of GT strength distributions for odd-A nuclei without relying on the Brink-Axel hypothesis, enhancing presupernova simulation accuracy.

Findings

Calculated decay rates agree with shell model results

Emphasized the role of nuclear deformation in weak decay calculations

Performed microscopic GT strength distribution calculations for all parent excited states

Abstract

Calculating weak decay rates under stellar conditions for studying presupernova evolution of massive stars is a challenging task. Here we show the importance of odd A nuclei for presupernova simulations. In order to calculate the required nuclear matrix elements we apply the pn QRPA model in a deformed basis. Nuclear deformation, thought to play an integral role in calculation of associated weak decay rates, is taken into account in our model. We calculate Gamow Teller (GT) strength distributions, emission and positron capture rates for selected odd A nuclei. Our model does not employ the Brink Axel hypothesis as used in previous calculations of weak decay rates and we perform a state by state microscopic calculation of GT strength distributions from all parent excited states. Our calculated decay rates are in good agreement with large scale shell model calculations.