Multi-quasiparticle states in 179Ta and structural changes in the yrast line of the odd tantalum isotopes

High-spin states in Ta have been studied by a variety of γ-ray spectroscopic techniques following the Yb(Li,4n) reaction. The new results independently confirm and extend the one-, three-and five- quasiparticle bands proposed previously. The more comprehensive results obtained allow firm spin assignments to be made and also the identification of rotational bands associated with the higher seniority intrinsic states. Configuration assignments follow from analysis of these rotational band properties. To explain changes in the yrast line across the chain of isotopes from Ta to Ta, multi-quasiparticle calculations have been performed and compared with experiment. The calculations, which treat pairing correlations using the Lipkin-Nogami approach and include blocking, incorporate single-particle energies adjusted to reproduce the observed one-quasiparticle bandheads. Properties specific to Ta include evidence for configuration mixing in the 21/2 isomer configuration. Its decay is one of several anomalously fast K-hindered transitions observed and discussed in terms of configuration changes and other mechanisms