Investigation of Weak Rates for Odd-A Nuclei for Presupernova Simulations

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, $$\beta ^-$$ 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 $$\beta ^-$$ decay rates are in good agreement with large-scale shell model calculations.