Thermal Equilibration of 176-Lu via K-Mixing

TL;DR

This paper investigates how K-mixing influences the thermal equilibration of 176-Lu in astrophysical environments, affecting its effective stellar half-life and implications for nucleosynthesis modeling.

Contribution

It introduces a model estimating gamma-decay rates enhanced by K-mixing and demonstrates its impact on the thermal equilibrium of 176-Lu in stellar conditions.

Findings

K-mixing significantly enhances gamma-decay rates near 725 keV

Even minimal K-mixing leads to quasi-equilibrium of 176-Lu during s-process

K-mixing affects the effective stellar half-life of 176-Lu

Abstract

In astrophysical environments, the long-lived (\T_1/2 = 37.6 Gy) ground state of 176-Lu can communicate with a short-lived (T_1/2 = 3.664 h) isomeric level through thermal excitations. Thus, the lifetime of 176-Lu in an astrophysical environment can be quite different than in the laboratory. We examine the possibility that the rate of equilibration can be enhanced via K-mixing of two levels near E_x = 725 keV and estimate the relevant gamma-decay rates. We use this result to illustrate the effect of K-mixing on the effective stellar half-life. We also present a network calculation that includes the equilibrating transitions allowed by K-mixing. Even a small amount of K-mixing will ensure that 176-Lu reaches at least a quasi-equilibrium during an s-process triggered by the 22-Ne neutron source.