Weak decays in superheavy nuclei

TL;DR

This study investigates electron capture and beta decay processes in superheavy nuclei using advanced relativistic nuclear models, revealing dominant forbidden transitions and identifying nuclei with significant electron capture branching ratios.

Contribution

It introduces a comprehensive relativistic theoretical framework to analyze decay modes in superheavy nuclei, emphasizing forbidden transitions and electron capture dominance.

Findings

First-forbidden $1^-$ transitions dominate decay rates.

Electron capture exceeds $eta^+$ decay in proton-rich nuclei.

44 nuclei have significant electron capture branching ratios (>5%).

Abstract

Superheavy nuclei represent the heaviest atoms and nuclides known at the limit of mass and charge. The observed superheavy nuclei are all proton-rich; they decay primarily by emitting $\alpha$ particles and fission, with a possible small electron capture (EC) branch. Due to the huge atomic numbers and associated relativistic effects, EC-decays of superheavy systems are expected to differ from what is known in lighter nuclei. In this paper, using the quantified relativistic nuclear density functional theory and the quasiparticle random-phase approximation with the interaction optimized to experimental $\beta^-$-decay half-lives and Gamow-Teller resonance energies, we study the EC/$\beta^\pm$-decays in $Z = 101-118$ nuclei. Both allowed ($1^+$) and first-forbidden ($0^-, 1^-$ and $2^-$) transitions are considered. We show that the first-forbidden $1^-$ transitions dominate the decay rates in almost all studied nuclei. For proton-rich nuclei, EC dominates over $\beta^+$ decay. We identify 44 nuclei with EC/$\beta^+$ branching ratio larger than 5\%, indicating a possible competition with $\alpha$-decay and spontaneous fission channels.