Level Structure ofHf178

Abstract

The level structure of ${}_{}{}^{178}{}_{}{}^{}\mathrm{Hf}$ has been studied via $\gamma$ singles, $\gamma -\gamma$ coincidences in the 2048 × 4096 channel mode, and $\gamma -\gamma$ directional-correlation measurements with Ge(Li) detectors from the decay of ${}_{}{}^{178}{}_{}{}^{}\mathrm{Ta}$. These data yielded 7 new transitions and the addition of 13 transitions to the decay scheme, which includes 5 new levels. The following levels were observed (energies in keV followed by the spin and parity): 93.13, $2^{+}$; 306.52, $4^{+}$; 1174.64, $2^{+}$; 1199.24, $0^{+}$; 1276.54, $2^{+}$; 1309.91, $1^{\pm }$, $2^{+}$; 1362.36, $2^{\mathrm{}(-)\mathrm{}}$; 1433.97, $0^{+}$; 1443.86, $0^{+}$; 1496.02, $2^{+}$; 1513.64, $1^{\pm }$, $2^{+}$; 1561.27, $2^{+}$; 1566.45, $1^{\pm }$, $2^{\pm }$; and 1771.95, $0^{+}$. $\gamma -\gamma$ directional correlations were measured with the $2^{+}$ → $0^{+}$, 93.13-keV transition and eight transitions that feed the first excited state. From the $\gamma -\gamma \left(\theta \right)$ data, spins of 2 and 0 are established for the 1362.36-and 1771.95-keV levels and $M1\mathrm{}$ admixtures of ${85.6}_{-1.7\mathrm{}}^{+1.2\mathrm{}}$ and 65.2 ± 3.2% for the 1183.40- and 1402.87-keV transitions. With these multipole admixtures, the branching ratios for the $K^{\pi }I=0^{+}2$, 1276.54-keV level cannot be brought into agreement with theory for a single $Z_{\beta }$ band-mixing parameter; while for the $K^{\pi }I=0^{+}2$, 1496.02-keV level they can be.