New Band-Mixing Anomalies inHf178

Abstract

$\gamma -\gamma \left(\theta \right)$ measurements with a NaI-Ge(Li) detector arrangement were carried out to measure the $M1\mathrm{}$ admixture in the 1183-keV, $2^{+}\to 2^{+}$ transition in ${}_{}{}^{178}{}_{}{}^{}\mathrm{Hf}$. These results yield $M1=\left({85.6}_{-2.1\mathrm{}}^{+1.1\mathrm{}}\right)\%$ 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 $Z_{\beta }$ value from the different branching ratios if a (73.0 ± 1.3)% $M1\mathrm{}$ admixture is assumed in the $2^{+}\to 2^{+}$ transition. Thus the measured $M1\mathrm{}$ admixture yields branching ratios that are not explained by the present band-mixing picture in contrast to earlier reports.