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

A four quasiparticle high-K isomer with a meanlife of 45~2! ms has been identified at 1451 keV in Ta, populated in the Yb(B,a3n! Ta 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, a difference which can be attributed partly to a change from the p9/2@514#n9/2 @624#7/2@514#5/2@512# configuration in Ta to the p9/2@514#7/2@404#5/2@402#n9/2@624# configuration in Ta. The reduced hindrance factors for E2 decays from related four-quasiparticle isomers in the isotopes Ta match the hindrances of the corresponding E2 decays from component 6 core states in the hafnium isotopes, Hf .