High-K Isomers In W-176 And Mechanisms Of K Violation

An isomer, with t(1/2)=35+/-10 ns and J,K-pi=14,14(+), has been observed in the nucleus W-176 using the reaction Nd-150(Si-30,4n) at a beam energy of 133 MeV The isomer exhibits an unusual pattern of decay in which the majority of the flux proceeds directly to states with [K]=0, bypassing available levels of intermediate K. This severe breakdown of normal K-selection rules in W-176 is compared with recent observations of K violation in neighboring nuclei, within the framework of proposed theoretical approaches. The available data on these K-violating decays seem to have a consistent explanation in models of K mixing which include large-amplitude fluctuations of the nuclear shape.