Multi-quasiparticle isomers and rotational bands in Re-181

High-spin states in Re-181 have been populated using the Yb-176(B-11, 6n) r eaction and their decays studied using the CAESAR gamma-ray spectrometer. T hirteen bands of rotational states have been observed based on 1-, 3- and 5 -quasiparticle structures, including two new 5-quasiparticle isomers, with half-lives of 1.2 mu s and 22 ns. Angular correlation and distribution coef ficients were obtained and gamma-ray intensity ratios were used to extract \g(K) - g(R)\/Q(0) ratios. Three K-forbidden decays were observed and their reduced hindrance factors were obtained and found to be consistent with kn own systematic behaviour. Band crossings were observed between 1- and 3-qua siparticle bands. These rotation-aligned 3-quasiparticle bands appear to ha ve high K, and are identified as t-bands. Band mixing calculations support the assigned K-values. A unique degeneracy was observed for two I-pi = 23/2 (-) states at 1883 keV. (C) 2000 Elsevier Science B.V. All rights reserved.