Rotational and intrinsic states above the Kπ=25/2-, T1/2=25 day isomer in 179Hf

Time-correlated, particle-tagged γ spectroscopy of the stable nucleus Hf was undertaken with incomplete fusion reactions initiated by beams of Be and Li incident on targets of Yb. Intrinsic and rotational states above the three-quasiparticle K=25/2, T=25 day isomer, Hf, are reported. The rotational band based on Hf has g-g values that are consistent with the previously suggested ν9/2 ⊗π[7/2,9/2] configuration assignment. A value of g=0.34(5) was derived for the collective g factor of Hf, which is considerably higher than that found for the 9/2 ground state. The difference is consistent with a reduction of the proton pairing strength due to blocking in the K=25/2 ν⊗π configuration. A number of νπ five-quasiparticle configurations were identified, the highest of which is an yrast K =43/2, T=15(5) μs isomer. It decays to an yrast K=39/2 state, which in turn decays to a rotational band based on a K=33/2 state. The K=33/2 state decays to the rotational band associated with Hf. Semiempirical calculations reproduce the excitation energies of the three-and five-quasiparticle states above Hf to within ∼200 keV. The calculations predict that the lowest seven-quasiparticle state will arise from a νπ configuration with K=47/2, which is just beyond the maximum spin accessible with the reactions employed here