Inelastic excitation of new high-spin yrast isomers in180Ta

Abstract

For the first time, six-quasiparticle isomers have been observed in the meta-stable nucleus ${}_{ 73}^{180}{\mathrm{Ta}}_{107}.$ Two new high-spin isomers were populated following deep-inelastic reactions with a pulsed ${}_{ 92}^{238}\mathrm{U}$ beam incident on a thick ${}_{ 72}^{180}\mathrm{Hf}$ target. Out-of-beam $\ensuremath{\gamma}$-ray events were collected using the Gammasphere germanium detector array. In addition to the known four-quasiparticle isomers, yrast ${K}^{\ensuremath{\pi}}{=(22}^{\ensuremath{-}})$ and $K>~23$ six-quasiparticle isomers have been observed with microsecond half-lives. These are the highest-spin isomers observed using the technique of deep-inelastic excitation. The assignments are compared to predictions made by BCS and Lipkin-Nogami multiquasiparticle calculations.