Properties of the 5- state at 839 keV in 176Lu and the s-process branching at A = 176

TL;DR

This paper investigates the properties of the 839 keV state in 176Lu and its role in the s-process branching at A=176, revealing a stronger coupling between states than previously thought, impacting nucleosynthesis models.

Contribution

It provides new experimental data and analysis on the 839 keV intermediate state, showing a significantly stronger coupling in 176Lu than earlier estimates.

Findings

Coupling between high-K and low-K states is at least ten times stronger than previously assumed.

Revised coupling affects the use of 176Lu/176Hf as an s-process thermometer.

Properties of additional candidate states are briefly analyzed.

Abstract

The s-process branching at mass number A = 176 depends on the coupling between the high-K ground state and a low-lying low-K isomer in 176Lu. This coupling is based on electromagnetic transitions via intermediate states at higher energies. The properties of the lowest experimentally confirmed intermediate state at 839 keV are reviewed, and the transition rate between low-K and high-K states under stellar conditions is calculated on the basis of new experimental data for the 839 keV state. Properties of further candidates for intermediate states are briefly analyzed. It is found that the coupling between the high-K ground state and the low-K isomer in 176Lu is at least one order of magnitude stronger than previously assumed leading to crucial consequences for the interpretation of the 176Lu/176Hf pair as an s-process thermometer.