High-spin states in ${}^{177}\mathrm{Ta}$ have been studied using the ${}^{170}\mathrm{Er}{(}^{11}\mathrm{B},4n)$ reaction. New intrinsic states have been observed corresponding to 3-, 5-, and 7-quasiparticle high-$K$ structures. Rotational bands built on most of the 3- and 5-quasiparticle states and some transitions above the 7-quasiparticle states have been identified. Several isomers have been found, the longest lived being the ${\frac{49}{2}}^{-},$ 7-quasiparticle state with a meanlife of 192 $\mu \mathrm{s}.$ Configurations for the observed intrinsic states have been assigned on the basis of $g_K$ values, alignments, and decay properties. While the properties of most of the bands are consistent with their proposed configurations, the behavior of some, including the one built on $K^{\pi }={\frac{21}{2}}^{-}$ 3-quasiparticle isomer, is not well understood. Multiquasiparticle blocking calculations based on the Lipkin-Nogami method, are in good agreement with the excitation energies of the experimentally observed states and all the predicted states close to the yrast line up to spin $\frac{49}{2}$ have been observed experimentally. The calculations predict the existence of a 9-quasiparticle ${\frac{67}{2}}^{-}$ yrast trap at $\sim 8.5\hspace{0.5em}\mathrm{MeV}.$

• Received 15 November 1999

DOI:https://doi.org/10.1103/PhysRevC.61.044321