Unique first-forbidden $\beta$-decay rates for neutron-rich nickel and zinc isotopes in stellar matter

The structure of neutron-rich nuclei has grown interest with the development of modern techniques enabling access to the exotic regions of the nuclide chart. In astrophysical environments, when allowed Gamow-Teller(GT) transitions are unfavored, first-forbidden transitions become important especially in medium heavy and heavy nuclei. Particularly in case of neutron-rich nuclei, GT transitions tend to be Pauli blocked and first-forbidden transitions are favored. In this meeting I would like to present the microscopic calculation of unique first-forbidden stellar $\beta$-decay rates and the associated $\beta$-decay half-lives for a number of neutron-rich nickel and zinc isotopes using the pn-QRPA theory. Comparison of the total half-lives will also be made with the measured half-lives and other theoretical calculations wherever possible. The temperature and density profiles were chosen for the advanced nuclear burning stages of the presupernova and supernova star. The results for total beta decay half-lives, for these neutron-rich nuclei, are found to be in much better agreement with the measured results and show marked improvement over the calculated half-lives where only allowed GT transitions were considered. The calculated rates are of special importance for core-collapse simu