K-hindered decay of a six-quasiparticle isomer in 176Hf

The structure and decay properties of high-K isomers in Hf-176 have been studied using beam sweeping techniques and the Gammasphere multidetector array. A new Delta K = 8 decay branch, from a K-pi = 22(-), six-quasiparticle, isomeric (t(1/2) = 43 mu s) state at 4864 keV to the 20(-) state of a K-pi = 14(-) band, has been identified. The reduced hindrance factor per degree of K forbiddenness for this decay is measured to be unusually low (f(nu) = 3.2), which suggests K mixing in the states involved. The deduced interaction matrix elements are discussed within the context of relevant K-mixing scenarios. The 3266-keV state, previously interpreted as a K-pi = 16(+) intrinsic state, is reassigned as the J(pi) = 16(+) member of the band based on the K-pi = 15(+) state at 3080 keV. The systematics of f(nu) values as a function of the degree of forbiddenness is discussed in light of this change.