Beta-decay half-lives of the isotopes close to the neutron drip line and astrophysical implications

Abstract

In this paper, we examined the β--decay half-lives of 94 extremely neutron-rich isotopes with Z = 26 − 57 close to the neutron drip line, which are important for the r-process calculations. The half-lives were calculated using four semi-empirical models and compared to those based on the FRDM+QRPA approach and available measured data. The impact of the difference in the models on the half-life predictions was investigated. We found that theoretical calculations for the β-decay half-life have a large deviation, up to 60%, which is mostly similar to that in measurements. The half-lives of the investigated nuclei are ranging from a few to hundreds of milliseconds. The r-process abundances in various astrophysical scenarios were calculated by using the predicted half-lives. The half-life uncertainty due to different models results in a large deviation in the isotopic abundance, specially for the isotopes in the mass range of A > 210. The shell closures in 76Fe is still a doubt due to the discrepancy in the trends of the half-life and paring gap while a closed-shell at N = 82 in 127Rh is possible. The results of this study also notice that it is a challenge for measuring precisely the masses of 106Rb, 116,117Nb, 122Tc, and 128Rh because of their short half-lives.