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

Abstract

A four quasiparticle high-{ital K} isomer with a meanlife of 45(2) {mu}s has been identified at 1451 keV in {sup 180}Ta, populated in the {sup 176}Yb({sup 11}B,{alpha}3{ital n}){sup 180}Ta reaction. The isomer decays into a rotational band which is associated with the two-quasiparticle 9{sup {minus}} isomer at 75.3 keV. Analysis of the branching ratios within that band and the magnetic moment for the 9{sup {minus}} isomer, supports the configuration assignment to the 9{sup {minus}} isomer. The {ital K} hindrance for the {ital E}2 decay of the 15{sup {minus}} isomer to the 9{sup {minus}} band is substantially lower than that for an apparently similar 15{sup {minus}} isomer in {sup 178}Ta, a difference which can be attributed partly to a change from the {pi}9/2{sup {minus}}[514]{nu}{sup 3}9/2{sup +} [624]7/2{sup {minus}}[514]5/2{sup {minus}}[512] configuration in {sup 178}Ta to the {pi}{sup 3}9/2{sup {minus}}[514]7/2{sup +}[404]5/2{sup +}[402]{nu}9/2{sup +}[624] configuration in {sup 180}Ta. The reduced hindrance factors for {ital E}2 decays from related four-quasiparticle isomers in the isotopes {sup 176,178,180}Ta match the hindrances of the corresponding {ital E}2 decays from component 6{sup +} core states in the hafnium isotopes, {sup 174,176,178}Hf. {copyright} {ital 1996 The American Physical Society.}