Intrinsic states and collective structures in180Ta

Abstract

Excited states in ${}^{180}\mathrm{Ta}$ have been identified using the ${}^{176}\mathrm{Yb}{(}^{11}\mathrm{B},\ensuremath{\alpha}{3n)}^{180}\mathrm{Ta}$ and ${}^{176}\mathrm{Yb}{(}^{7}\mathrm{Li}{,3n)}^{180}\mathrm{Ta}$ reactions and associated time-correlated $\ensuremath{\gamma}$-ray spectroscopy, including particle-$\ensuremath{\gamma}$ coincidences for channel selection. As well as identifying the rotational band based on the ${9}^{\ensuremath{-}}$ two-quasiparticle state at 75 keV, at least eight other low-lying two-quasiparticle states and associated rotational bands have been established. Lifetimes in the few nanosecond region were isolated using $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$-time techniques. Most of the observed two-quasiparticle states and some of the band members can be identified with states known from particle transfer studies. The properties of the observed ${\ensuremath{\Omega}}_{n}\ifmmode\pm\else\textpm\fi{}{\ensuremath{\Omega}}_{p}$ partners of ${1}^{+}$ and ${8}^{+}$ bands from the $\ensuremath{\nu}{9/2}^{+}[624]\ensuremath{\bigotimes}\ensuremath{\pi}{7/2}^{+}[404]$ configuration and the ${0}^{\ensuremath{-}}$ and ${9}^{\ensuremath{-}}$ pair from the $\ensuremath{\nu}{9/2}^{+}[624]\ensuremath{\bigotimes}\ensuremath{\pi}{9/2}^{\ensuremath{-}}[514]$ configuration are discussed. High-$K$ structures identified include the band based on the four-quasiparticle $45 \ensuremath{\mu}\mathrm{s}$, ${15}^{\ensuremath{-}}$ isomer, a 32 ns, four-quasiparticle ${18}^{(+)}$ isomer, and a six-quasiparticle ${19}^{(\ensuremath{-})}$ intrinsic state and its band. Configuration assignments are aided by analysis of the in-band decay properties, which confirm, for example, a predominantly $\ensuremath{\nu}{\ensuremath{\pi}}^{3}$ configuration for the ${15}^{\ensuremath{-}}$ isomer. The results are compared with multiquasiparticle calculations. A number of yrast high-$K$ six- and eight-quasiparticle states which could be accessible in future studies are predicted.