Competing phenomena: high-seniority excitations and γ-softness in 184Os.

The nuclear structure of the stable nucleus 18476Os has been studied including five newly identified rotational bands built on 2-quasiparticle Kπ=0+, 6−, 8− couplings. The excitation energies of the proposed multi-quasiparticle excitations are in good agreement with predictions of blocked BCS calculations. The interaction responsible for the first band crossing, caused by a high-K tilted 2-neutron configuration, is calculated and a new interpretation presented for the yrast states after the interaction. A second crossing with an aligned s–β band is also reported. The yrast behaviour at high spins is dominated by a wealth of short-lived (nanoseconds and shorter) high-K levels. The low reduced hindrances for intrinsic state decays are discussed, and attributed to the triaxial shapes and fluctuations predicted by configuration-constrained potential-energy-surface calculations. Comparisons with neighbouring nuclei are made. [Copyright &y& Elsevier]