Approaching the precursor nuclei of the third r-process peak with RIBs

TL;DR

This paper reports experimental measurements of neutron-rich nuclei relevant to the third r-process peak, highlighting the importance of accurate decay data for improving nucleosynthesis models and emphasizing the need for further measurements around N~126.

Contribution

It provides new experimental data on decay properties of neutron-rich nuclei near N~126, and discusses their impact on r-process abundance predictions.

Findings

Half-lives and neutron branching ratios are smaller than previous models suggest.

Uncertainties in decay data significantly affect r-process abundance calculations.

Additional measurements are needed for more accurate nuclear structure modeling.

Abstract

The rapid neutron nucleosynthesis process involves an enormous amount of very exotic neutron-rich nuclei, which represent a theoretical and experimental challenge. Two of the main decay properties that affect the final abundance distribution the most are half-lives and neutron branching ratios. Using fragmentation of a primary $^{238}$U beam at GSI we were able to measure such properties for several neutron-rich nuclei from $^{208}$Hg to $^{218}$Pb. This contribution provides a short update on the status of the data analysis of this experiment, together with a compilation of the latest results published in this mass region, both experimental and theoretical. The impact of the uncertainties connected with the beta-decay rates and with beta-delayed neutron emission is illustrated on the basis of $r$-process network calculations. In order to obtain a reasonable reproduction of the third $r$-process peak, it is expected that both half-lives and neutron branching ratios are substantially smaller, than those based on FRDM+QRPA, commonly used in $r$-process model calculations. Further measurements around $N\sim126$ are required for a reliable modelling of the underlying nuclear structure, and for performing more realistic $r$-process abundance calculations.