Structure of positive-parity yrast band in Br-80

The states of the positive-parity yrast band in Br-80 have been investigate d using the Ge-76(Li-7, 3n gamma) reaction at a beam energy of 32 MeV. The band has been extended up to 4450 keV with a spin of (14(+)). Unambiguous s pin assignments are made for states up to 2944.0 keV and gamma-ray multipol e mixing ratios are determined for several Delta J = 1 transitions. Lifetim es studies for the 10(+), 11(+) and 12(+) states provide an estimate of the quadrupole deformation in this band. Cranking model analysis of the experi mental data reveals a signature inversion at a spin of 12 h and a probable neutron alignment at h omega approximate to 0.7 MeV. The results are discus sed within the framework of the Systematics of similar bands in the lighter Br isotopes and the cranked-shell model. In addition, a new positive-parit y and two negative-parity sequences have been identified. (C) 2000 Elsevier Science B.V. All rights reserved.