Evidence for a high-spin beta-decaying isomer in Lu-177

Nuclei in the A similar to 180 region have been populated and investigated in a series of multinucleon transfer and deep-inelastic reactions involving an 11.4 MeV per nucleon Xe-136 beam produced by the GSI UNILAC accelerator, impinging on a selection of tantalum and tungsten targets. The reaction products were released from a thermal ion source and subsequently mass selected using the GSI on-line mass separator. The unexpectedly high yield of gamma rays associated with the decay of the well established K-pi=37/2(-),t(1/2)=51.4 min isomer in Hf-177(72) and anomalous half-life characteristics associated with this decay lead to these data being interpreted as the beta(-) decay of a high-K isomer in the mother nucleus, Lu-177. By comparing the experimental findings with the predictions obtained from multi-quasiparticle blocked-BCS-Nilsson calculations, the proposed decay is suggested to be from a K-pi=39/2(-) five-quasiparticle state in Lu-177(71). A half-life of 7 +/- 2 min is determined for this beta-decay path which is estimated to have an excitation energy of approximate to3.9 MeV above the Lu-177 ground state.