Gamow-Teller transitions of neutron-rich N = 82,81 nuclei by shell-model calculations

Abstract

β-decay half-lives of neutron-rich nuclei around N=82 are key data to understand the r-process nucleosynthesis. We performed large-scale shell-model calculations in this region using a newly constructed shell-model Hamiltonian, and successfully described the low-lying spectra and half-lives of neutron-rich N=82 and N=81 isotones with Z=42-49 in a unified way. We found that their Gamow-Teller strength distributions have a peak in the low excitation energies, which significantly contributes to the half-lives. This peak, dominated by ν0g7/2 → π0g9/2 transitions, is enhanced on the proton-deficient side because the Pauli-blocking effect caused by occupying the valence proton 0g9/2 orbit is weakened.