Structure and decay of a four-quasiparticle 15(-) isomer in Ta-180

A four quasiparticle high-K isomer with a meanlife of 45(2) mu s has been identified at 1451 keV in Ta-180, populated in the Yb-176(B-11,alpha 3n) Ta-180 reaction. The isomer decays into a rotational band which is associated with the two-quasiparticle 9(-) isomer at 75.3 keV. Analysis of the branching ratios within that band and the magnetic moment for the 9(-) isomer, supports the configuration assignment to the 9(-) isomer. The K hindrance for the E2 decay of the 15(-) isomer to the 9(-) band is substantially lower than that for an apparently similar 15(-) isomer in Ta-178, a difference which can be attributed partly to a change from the pi 9/2(-)[514]nu(3)9/2(+) [624]7/2(-)[514]5/2(-)[512] configuration in Ta-178 to the pi(3)9/2(-)[514]7/2(+)[404]5/2(+)[402]nu 9/2(+)[624] configuration in Ta-180. The reduced hindrance factors for E2 decays from related four-quasiparticle isomers in the isotopes Ta-176,Ta-178,Ta-180 match the hindrances of the corresponding E2 decays from component 6(+) core states in the hafnium isotopes, Hf-174,Hf-176,Hf-178.