Configuration changes and hindered decays in four- and six-quasiparticle isomers in Ta178

A six-quasiparticle isomer with K-pi=21(-), a half-life of 290(12) ms, and the pi(3) nu(3) configuration has been identified in the odd-odd nucleus Ta-178, at an excitation energy of 2902 keV. The rotational bands built on the known K-pi=15(-). Isomer and on the newly found 16(+) four-quasiparticle and 22(+) six-quasiparticle states, have also been identified, allowing characterization of the configurations. The 15(-) band is predominantly of pi nu(3) character with a pi nu(3) admixture. When the mixing is taken into account the excitation energies of the main yrast multi-quasiparticle states can be reproduced. The multi-quasiparticle states observed are related essentially through the addition of the two-quasiparticle component nu(2) [6(+)] or pi(2) [6(+)]. Depending on whether the transition between the states involves the change nu(2) [6(+)]-->[0] or pi(2) [6(+)]-->[0], the E2 hindrance factors for decays between the six- and four-quasiparticle stares are relatively large or small. This dependence mimics the pattern observed in the two-quasiparticle core transitions and, because the 15(-) isomer is mainly pi nu(3), the magnitude sequence is inverted compared to that observed in Ta-176.