Multi-quasiparticle states and K-forbidden transitions in 183Os

Abstract

High-spin states in 183Os have been studied using the 170Er( 18O, 5n) reaction at a beam energy of 85 MeV. Nine rotational bands based on 1-, 3-, 5- and 7-quasiparticle excitations have been observed. Nilsson configurations are assigned for the newly observed bands using g-factors deduced from M1/E2 branching ratios within the bands. In addition, two isomers with K π =(43/2 +) and (43/2 −) have been identified. The K π =(43/2 +) isomer decays directly to the K π =9/2 + ground-state band with a large difference in the K quantum number, ΔK=17. The decay rates are discussed in terms of a tunneling model where high- K (isomeric) and low- K states interact via fluctuations towards triaxial nuclear shapes.