Validity of Brink Axel Hypothesis for calculations of allowed stellar weak rates of heavy nuclei

TL;DR

This paper evaluates the validity of the Brink-Axel hypothesis in calculating stellar weak rates of heavy nuclei, which are crucial for understanding nucleosynthesis in explosive stellar environments.

Contribution

It critically assesses the applicability of the Brink-Axel hypothesis for modeling Gamow-Teller strength functions in astrophysical nuclear reaction calculations.

Findings

The Brink-Axel hypothesis may not always hold for excited nuclear states.

Dependence of strength functions on parent state details can impact stellar rate calculations.

Results suggest potential limitations of the BA hypothesis in certain nuclear conditions.

Abstract

The knowledge of beta decay transitional probabilities and GamowTeller (GT) strength functions from highly excited states of nuclides is of particular importance for applications to astrophysical network calculations of nucleosynthesis in explosive stellar events. These quantities are challenging to achieve from measurements or computations using various nuclear models. Due to unavailability of feasible alternatives, many theoretical studies often rely on the Brink Axel (BA) hypothesis, that is, the response of strength functions depends merely on the transition energy of the parent nuclear ground state and is independent of the underlying details of the parent state, for the calculation of stellar rates. BA hypothesis has been used in many applications from nuclear structure determination to nucleosynthesis yield in the astrophysical matter.