Modification of nuclear transitions in stellar plasma by electronic processes: K-isomers in 176Lu and 180Ta under s-process conditions

TL;DR

This study investigates how stellar plasma affects nuclear transitions in 176Lu and 180Ta, finding that low-energy transitions are significantly enhanced mainly by electron capture, but overall nucleosynthesis remains unaffected.

Contribution

It demonstrates that electron capture significantly enhances low-energy nuclear transitions in stellar plasma, with minimal impact on the s-process nucleosynthesis of 176Lu and 180Ta.

Findings

Low-energy transitions below 100 keV are significantly enhanced.

Transitions above 200 keV are practically unaffected.

Overall s-process nucleosynthesis of 176Lu and 180Ta remains unchanged.

Abstract

The influence of the stellar plasma on the production and destruction of K-isomers is studied for the examples 176Lu and 180Ta. Individual electromagnetic transitions are enhanced predominantly by nuclear excitation by electron capture, whereas the other mechanisms of electron scattering and nuclear excitation by electron transition give only minor contributions. It is found that individual transitions can be enhanced significantly for low transition energies below 100 keV. Transitions with higher energies above 200 keV are practically not affected. Although one low-energy transition in 180Ta is enhanced by up to a factor of 10, the stellar transition rates from low-K to high-K states via so-called intermediate states in 176Lu and 180Ta do not change significantly under s-process conditions. The s-process nucleosynthesis of 176Lu and 180Ta remains essentially unchanged.