Mixing effects on K-forbidden transition rates from the 6 isomers in the N = 104 isotones

The problem of the very different E2 decay rates from the two-quasineutron K = 6 isomers in the N = 104 isotones Er, Yb, Hf, and W is investigated using the triaxial projected shell model with inclusion of multi-quasiparticle configurations. It is demonstrated that the highly K-forbidden transition from the 6 isomer to the ground-state band is sensitive to mixing with the 6 state of the γ-vibrational band. Thus the inter-band transitions, and lifetimes, depend on the relative position of the γ-band and the isomeric state in each isotone. © 2013 IOP Publishing Ltd