First access to beta half-lives approaching the r-process path near N=126

TL;DR

This study reports the first measurements of beta-decay half-lives of neutron-rich nuclei near N=126, providing insights into r-process nucleosynthesis and highlighting the significance of first-forbidden transitions.

Contribution

It presents new experimental half-life data for nuclei near N=126 and compares these with advanced models, emphasizing the role of first-forbidden decays.

Findings

Beta-decay half-lives of 8 nuclides measured near N=126.

Data suggest faster matter flow in the r-process than previously thought.

Indications of the importance of first-forbidden transitions around A=195.

Abstract

Heavy neutron-rich nuclei close to N=126 were produced by fragmentation of a 1 A GeV 208Pb beam at the FRS at GSI. The beta-decay half-lives of 8 nuclides have been determined. The comparison of the data with model calculations including an approach based on the self-consistent ground-state description and continuum QRPA considering the Gamow-Teller and first-forbidden decays provide a first indication on the importance of first-forbidden transitions around A=195. The measured data indicate that the matter flow in the r-process to heavier fissioning nuclei is faster than previously expected.