Shell-model description for the first-forbidden $β^-$ decay of ${}^{207}$Hg into the one-proton-hole nucleus ${}^{207}$Tl

Abstract

In this work, we have performed large-scale shell-model calculations for the first-forbidden $β^{-}$ decay of ${}^{207}$Hg into the one-proton-hole nucleus ${}^{207}$Tl corresponding to the recently available experimental data from ISOLDE-CERN [T. A. Berry et al., Phys. Rev. C 101, 054311 (2020)]. We have used the one-particle one-hole ($1p$-$1h$) truncation for both protons and neutrons simultaneously across the doubly-shell closure at ${}^{208}$Pb in the final states of ${}^{207}$Tl. In our calculations, we have also considered the effect of mesonic enhancement $\hat{I}{\mu }_{\mathrm{mec}}=2.01\pm 0.05$ in the rank-0 for the axial-charge matrix element ${\hat{I}}_5^3$. Here, we have calculated the $\log ft$ values from the ground-state of ${}^{207}$Hg to the several excited states of ${}^{207}$Tl and obtained a good agreement between the calculated and the experimental data. In the experimental data spin and parity for some states are not yet confirmed, thus based on the shell-model results for the $\log ft$ values we have given the prediction for these states. This is the first theoretical calculation for the $\log ft$ values for these transitions.

16 pages, 2 figures, 2 tables