Impact of the first-forbidden $\beta$ decay on the production of $A \sim 195$ r-process peak

TL;DR

This study examines how first-forbidden beta decays influence the formation of the r-process abundance peak around mass number 195, highlighting their impact on decay rates and resulting element distribution.

Contribution

It provides a detailed analysis of the role of first-forbidden transitions and beta-delayed neutron emission in shaping the r-process peak, emphasizing the importance of accurate half-life data.

Findings

First-forbidden decays shorten beta-decay lifetimes for N~126 nuclei.

Including beta-delayed neutron emission broadens the abundance peak.

Effects are consistent across various astrophysical models.

Abstract

We investigated the effects of first-forbidden transitions in $\beta$ decays on the production of the r-process $A \sim 195$ peak. The theoretical calculated $\beta$-decay rates with $\beta$-delayed neutron emission were examined using several astrophysical conditions. As the first-borbidden decay is dominant in $N \sim 126$ neutron-rich nuclei, their inclusion shortens $\beta$-decay lifetimes and shifts the abundance peak towards higher masses. Additionally, the inclusion of the $\beta$-delayed neutron emission results in a wider abundance peak, and smoothens the mass distribution by removing the odd-even mass staggering. The effects are commonly seen in the results of all adopted astrophysical models. Nevertheless there are quantitative differences, indicating that remaining uncertainty in the determination of half-lives for $N=126$ nuclei is still significant in order to determine the production of the r-process peak.