Excited states in ${}^{165}\mathrm{Ta}$ were populated in the ${}^{142}\mathrm{Nd}{(}^{27}\mathrm{Al}{,4n)}^{165}\mathrm{Ta}$ and ${}^{141}\mathrm{Pr}{(}^{28}\mathrm{Si}{,4n)}^{165}\mathrm{Ta}$ reactions and investigated using the AFRODITE array. The yrast rotational decay sequence up to spin ${53/2}^{-}$ is identified and assigned to the $\left[514\right]{9/2}^{-}$ configuration. The nuclear shape is investigated using total Routhian surface calculations. The experimental results are discussed in relation to existing data in the neighboring Ta isotopes and results from cranked shell model calculations. Unexpectedly large signature splitting, for a high-$\Omega$ configuration, is observed in the yrast band. Further discrepancies are observed between theoretical and experimental values for the band crossing frequency and signature splitting of the $B\left(M1\mathrm{}\right)/B\left(E2\mathrm{}\right)\mathrm{}$ ratios. The possibility that these discrepancies are a consequence of a large deviation from an axially symmetric nuclear shape is investigated.

• Received 1 September 2000

DOI:https://doi.org/10.1103/PhysRevC.63.024303