High-spin states and K-forbidden decay in 172Hf.

Abstract

High-spin states were populated in $^{172}\mathrm{Hf}$ with the $^{48}\mathrm{Ca}$${+}^{128}$Te reaction at 200 and 214 MeV. All of the known rotational bands in $^{172}\mathrm{Hf}$ have been extended and five new rotational bands have been observed using the Gammasphere spectrometer. This study establishes the highest known state in $^{172}\mathrm{Hf}$ at spin 44\ensuremath{\Elzxh}. One of the new bands is a ${\mathit{K}}^{\mathrm{\ensuremath{\pi}}}$=(${14}^{+}$) strongly coupled rotational band. In conflict with the K-selection rule another newly established bandhead state, with spin I=K=12, is observed to \ensuremath{\gamma} decay directly to the yrast ${12}^{+}$ state. This large breakdown in the K-selection rule (\ensuremath{\Delta}K\ensuremath{\approxeq}12) may be due to a mixing between the low- and high-K states in $^{172}\mathrm{Hf}$.