Nuclear isomers and astrophysical reaction rates

How long-lived excited nuclear states influence element formation in stars

Abstract

Background: Nuclear metastable states that is isomers play a distinct roles in the nucleosynthesis of elements by altering reaction paths within stellar environments. Purpose: This study reviews the existing catalogue of nuclear isomers to analyse their influence on the astrophysically important s-process reaction rates. Methods: The work utilizes the database of s-process astrophysical reaction rates available at download.nucastro.org/astro/x/xfactors.txt. The focus is made on the nuclei where the ground state contributions could not fully constrain the nuclear reaction rates (metric X< 1) at temperatures relevant for astrophysical scenarios. These nuclei are further analyzed in terms of their spectroscopic properties using the Atlas of Nuclear Isomers. Results: A dataset of nuclei exhibiting X<1 at stellar temperatures (kT=30 and 80 keV) is compiled. Statistical analysis reveals a bimodal distribution in isomeric half-lives and a weak positive correlation between excitation energy and metric X, while half-life shows negligible correlation. Conclusions: The analysis suggests that the s-process reaction rates are more sensitive to isomeric excitation energies than to half-life of the state. Such insights are crucial for further research and measurements.