New Band-Mixing Anomalies inHf178

Abstract

$\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}(\ensuremath{\theta})$ measurements with a NaI-Ge(Li) detector arrangement were carried out to measure the $M1$ admixture in the 1183-keV, ${2}^{+}\ensuremath{\rightarrow}{2}^{+}$ transition in $^{178}\mathrm{Hf}$. These results yield $M1=({85.6}_{\ensuremath{-}2.1}^{+1.1})%$ for the 1183-keV transition. Accurate branching ratios were also obtained from singles spectra taken with a large-volume Ge(Li) detector. It is possible to obtain from these intensities the same ${Z}_{\ensuremath{\beta}}$ value from the different branching ratios if a (73.0 \ifmmode\pm\else\textpm\fi{} 1.3)% $M1$ admixture is assumed in the ${2}^{+}\ensuremath{\rightarrow}{2}^{+}$ transition. Thus the measured $M1$ admixture yields branching ratios that are not explained by the present band-mixing picture in contrast to earlier reports.