Contribution of excited states to stellar weak-interaction rates in odd-A nuclei

TL;DR

This study investigates how excited nuclear states influence weak-interaction rates like beta-decay and electron capture in odd-A nuclei under astrophysical conditions, finding their impact is minimal within model uncertainties.

Contribution

It introduces a detailed quasiparticle random-phase approximation approach to assess excited state contributions in weak processes for odd-A pf-shell nuclei.

Findings

Excited states contribute minimally to total rates.

Rates are similar to ground state rates within uncertainties.

Model dependence dominates rate uncertainties.

Abstract

Weak-interaction rates, including beta-decay and electron capture, are studied in several odd-A nuclei in the pf-shell region at various densities and temperatures of astrophysical interest. Special attention is paid to the relative contribution to these rates of thermally populated excited states in the decaying nucleus. The nuclear structure involved in the weak processes is studied within a quasiparticle random-phase approximation with residual interactions in both particle-hole and particle-particle channels on top of a deformed Skyrme Hartree-Fock mean field with pairing correlations. In the range of densities and temperatures considered, it is found that the total rates do not differ much from the rates of the ground state fully populated. In any case, the changes are not larger than the uncertainties due to the nuclear model dependence of the rates.