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

Abstract High-spin states in 183 Os have been studied using the 170 Er( 18 O, 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.