Shell-model half-lives for r-process waiting point nuclei including first-forbidden contributions

TL;DR

This study uses large-scale shell-model calculations to determine the half-lives and neutron-branching probabilities of r-process waiting point nuclei, incorporating both allowed and first-forbidden transitions, with results aligning well with experimental data.

Contribution

It introduces comprehensive shell-model calculations including first-forbidden transitions for key r-process nuclei, improving half-life predictions across multiple neutron magic numbers.

Findings

Good agreement with experimental half-lives for N=50 and N=82 nuclei.

Forbidden transitions significantly reduce half-lives at N=126.

Small effect of forbidden transitions on N=50 and N=82 nuclei.

Abstract

We have performed large-scale shell-model calculations of the half-lives and neutron-branching probabilities of the r-process waiting point nuclei at the magic neutron numbers N=50, 82, and 126. The calculations include contributions from allowed Gamow-Teller and first-forbidden transitions. We find good agreement with the measured half-lives for the N=50 nuclei with charge numbers Z=28-32 and for the N=82 nuclei 129Ag and 130Cd. The contribution of forbidden transitions reduce the half-lives of the N=126 waiting point nuclei significantly, while they have only a small effect on the half-lives of the N=50 and 82 r-process nuclei.