Allowed and unique first-forbidden stellar electron emission rates of neutron-rich copper isotopes

Abstract

The allowed charge-changing transitions are the most common weak interaction processes of spin-isospin form that play a crucial role in several nuclear/astrophysical processes. The first-forbidden (FF) transition becomes important, in the circumstances where allowed Gamow-Teller (GT) transitions are unfavored, specifically for neutron-rich nuclei due to phase space considerations. In this paper deformed proton-neutron quasi-particle random phase approximation (pn-QRPA) model is applied, for the first time, for the estimation of allowed GT and unique first-forbidden (U1F) transitions ( $|\Delta J| = 2$ ) of neutron rich copper isotopes in mass range $72 \leq A \leq 82$ under stellar conditions. We compared our computed terrestrial $\beta$ -decay half-life values with previous calculations and experimental results. It was concluded that the pn-QRPA calculation is in good accordance with measured data. Our study suggests that the addition of rank (0 and 1) operators in FF transitions can further improve the comparison which remain unattended at this stage. The deformed pn-QRPA model was employed for the estimation of GT and U1F stellar electron emission ( $\beta^{-}$ -decay) rates over wide range of stellar temperature (0.01 GK–30 GK) and density ( $10\mbox{--}10^{11}\mbox{ g}/\mbox{cm}^{3}$ ) domains for astrophysical applications. Our study shows that, in high density and low temperature regions, the contribution of U1F rates to total electron emission rates of neutron-rich copper nuclei is negligible.