M3andE4K-forbidden decays of theKπ=23/2−isomer in177Lu

Abstract

Decay of the long-lived (${T}_{1/2}=160.44$ d) ${K}^{\ensuremath{\pi}}=23/{2}^{\ensuremath{-}}$ isomer in ${}^{177}$Lu was investigated using a chemically purified source and the Gammasphere array. New, high-multipolarity M3 and E4 deexcitation branches to the known ${I}^{\ensuremath{\pi}}=17/{2}^{\ensuremath{-}}$ and 15/2${}^{\ensuremath{-}}$ members of the $\ensuremath{\pi}$9/2${}^{\ensuremath{-}}$[514] band were discovered. The reduced hindrance factors per degree of $K$ forbiddenness deduced for these two transitions are found to be relatively large when compared to similar decays from the ${K}^{\ensuremath{\pi}}=37/{2}^{\ensuremath{-}}$ (${T}_{1/2}=51.4$ min) and ${K}^{\ensuremath{\pi}}={16}^{+}$ (${T}_{1/2}=31$ yr) isomers in ${}^{177}$Hf and ${}^{178}$Hf, respectively. This is attributed to significant configuration changes that occur in the decay of this ${}^{177}$Lu isomer.