Detailed study of the decay of $^{21}$Mg

TL;DR

This study provides a detailed analysis of the decay modes of $^{21}$Mg, updating the decay scheme, confirming previous branches, and testing mirror symmetry through experimental measurements at CERN.

Contribution

It offers the first comprehensive decay scheme update for $^{21}$Mg, including new spin and parity assignments and beta strength distribution analysis.

Findings

Confirmed the $eta$p$ extalpha$ branch.

Measured a half-life of 120.5 ms for $^{21}$Mg.

Updated decay scheme and tested mirror symmetry.

Abstract

Beta-delayed proton and gamma emission in the decay of $^{21}$Mg has been measured at ISOLDE, CERN with the ISOLDE Decay Station (IDS) set-up. The existing decay scheme is updated, in particular what concerns proton transitions to excited states in $^{20}$Ne. Signatures of interference in several parts of the spectrum are used to settle spin and parity assignments to highly excited states in $^{21}$Na. The previously reported $\beta$p$\alpha$ branch is confirmed. A half-life of 120.5(4) ms is extracted for $^{21}$Mg. The revised decay scheme is employed to test mirror symmetry in the decay and to extract the beta strength distribution of $^{21}$Mg that is compared with theory.