Decays ofTa176,Lu176, andLu176mto Levels inHf176

The locations of 48 energy levels in ${}_{}{}^{176}{}_{}{}^{}\mathrm{Hf}$ have been deduced from $\gamma$-ray singles, conversion-electron, and $\gamma -\gamma$ coincidence measurements on the $\mathrm{E}\mathrm{C}-{\beta }^{+}$ decay of ${}_{}{}^{176}{}_{}{}^{}\mathrm{Ta}$. Over $300\gamma$-ray transitions have been observed in the ${}_{}{}^{176}{}_{}{}^{}\mathrm{Ta}$ decay spectrum, and about 140 of these have been definitely assigned to the ${}_{}{}^{176}{}_{}{}^{}\mathrm{Hf}$ level scheme on the basis of 75 $\gamma -\gamma$ coincidence spectra. Spin and parity assignments are proposed for 27 levels besides the ground-state rotationalband members. Less extensive $\gamma$-ray singles data from ${}_{}{}^{176}{}_{}{}^{}\mathrm{Lu}$ and ${}_{}{}^{176m}{}_{}{}^{}\mathrm{Lu}$ decay have also been obtained; these are found to be consistent with the ${}_{}{}^{176}{}_{}{}^{}\mathrm{Hf}$ level structure proposed on the basis of ${}_{}{}^{176}{}_{}{}^{}\mathrm{Ta}$ decay data. Two $0^{+}$ excitations in ${}_{}{}^{176}{}_{}{}^{}\mathrm{Hf}$ identified at 1150 and 1293 keV are found to display quite different decay properties. Evidence for the existence of a series of low-spin four-quasiparticle states near 3 MeV is cited. The ${}_{}{}^{176}{}_{}{}^{}\mathrm{Hf}$ level structure is compared with available theoretical calculations, and a preliminary interpretation of several unusual features of the level scheme is presented.