A novel method for stellar electron-capture rates of excited nuclear states

Abstract

We propose a novel shell-model method to calculate stellar electron-capture (EC) rates of highly-excited nuclear states. This method is based on the Projected Shell Model that can incorporate high-order multi-quasiparticle configurations in a large model space. By taking the EC calculation from 59Co to 59Fe as the first example, we study the effects of nuclear excitations (including both single-particle and collective excitations) on the stellar EC rates. It is found that the predicted EC rates exhibit large variations as functions of excitations in both parent and daughter nuclei, which sensitively depend on the density and temperature in the stellar environment. We emphasize the importance of inclusion of multi-quasiparticle configurations constructed in a large model space for the calculation of EC rates used in astrophysical studies.

Keywords

• Stellar electron-capture rates
• Gamow-Teller transitions
• Single-particle excitations
• Collective excitations
• Projected shell model