Statistical Hauser-Feshbach model description of $(n,\alpha)$ reaction cross sections for the weak s-process

Abstract

The $(n,\alpha)$ reaction contributes in many processes of energy generation and nucleosynthesis in stellar environment. Since experimental data are available for a limited number of nuclei and in restricted energy ranges, at present only theoretical studies can provide predictions for all astrophysically relevant $(n,\alpha)$ reaction cross sections. The purpose of this work is to study $(n,\alpha)$ reaction cross sections for a set of nuclei contributing in the weak s-process nucleosynthesis. Theory framework is based on the statistical Hauser-Feshbach model implemented in TALYS code with nuclear masses and level densities based on Skyrme energy density functional. In addition to the analysis of the properties of calculated $(n,\alpha)$ cross sections, the Maxwellian averaged cross sections are described and analyzed for the range of temperatures in stellar environment. Model calculations determined astrophysically relevant energy windows in which $(n,\alpha)$ reactions occur in stars. In order to reduce the uncertainties in modeling $(n,\alpha)$ reaction cross sections for the s-process, novel experimental studies are called for. Presented results on the effective energy windows for $(n,\alpha)$ reaction in weak s-process provide a guidance for the priority energy ranges in the future experimental studies.