Intrinsic states and rotational bands in ¹⁷⁶Ta and ¹⁷⁸Ta

Abstract

High-spin states in the deformed, doubly odd nuclei, ¹⁷⁶Ta and ¹⁷⁸Ta have been studied by time-correlated γ-ray and electron spectroscopy techniques following (HI,xn) reactions. The new results independently confirm and extend in spin the previously known two- and four-quasiparticle states, albeit with some differences. Many high-seniority structures, most of them with associated rotational bands, have been identified for the first time. Several high-K isomers with half-lives ranging from a few nanoseconds up to hundreds of milliseconds have been discovered. Observation of rotational bands, built upon the intrinsic states has allowed characterization of the configurations, through both the in-band decay properties and alignments. The excitation energies of the observed multi-quasiparticle structures are generally reproduced using calculations based on the Lipkin-Nogami pairing model with inclusion of the effects of blocking and empirical nucleon-nucleon interactions. Some discrepancies in the energies, such as for the 14⁻ and 15⁻ isomers in ¹⁷⁶Ta and ¹⁷⁸Ta, respectively, are attributed to specific configuration mixing. Several anomalously fast K-forbidden transitions are discussed.