Complete inclusion of parity-dependent level densities in the statistical description of astrophysical reaction rates

TL;DR

This paper introduces a method to incorporate full parity dependence of nuclear level densities into all stages of astrophysical reaction rate calculations, revealing significant differences from traditional models.

Contribution

It presents an indirect approach to include parity dependence throughout the reaction process, improving the accuracy of astrophysical reaction rate predictions.

Findings

Noticeable differences in neutron capture rates for Ni and Sn isotopes.

Parity dependence affects reaction rates even at higher excitation energies.

Standard equipartition assumptions may underestimate or misrepresent reaction rates.

Abstract

Microscopic calculations show a strong parity dependence of the nuclear level density at low excitation energy of a nucleus. Previously, this dependence has either been neglected or only implemented in the initial and final channels of Hauser-Feshbach calculations. We present an indirect way to account for a full parity dependence in all steps of a reaction, including the one of the compound nucleus formed in a reaction. To illustrate the impact on astrophysical reaction rates, we present rates for neutron captures in isotopic chains of Ni and Sn. Comparing with the standard assumption of equipartition of both parities, we find noticeable differences in the energy regime of astrophysical interest caused by the parity dependence of the nuclear level density found in the compound nucleus even at sizeable excitation energies.