Alignments and new band structures in the doubly odd nucleus 80Rb

Abstract

The high spin structure of 80Rb has been investigated using the reaction 51V( 32S,2pn) at a beam energy 105 MeV. The level scheme was established from γ-γ and recoil-γ-γ coincidence measurements obtained using the Gamma Detector Array consisting of eight Compton suppressed Ge detectors coupled to the recoil mass separator HIRA. Rotational states upto an excitation energy 13 MeV and a spin 25ħ were studied. Band crossings at ħω = 0.63 and 0.73 MeV in the negative parity band, due to successive g 9 2 proton and neutron alignment, were observed for the first time. Evidence has also been found for a hitherto unknown sideband. The yrast positive parity bands in 78Kr and 80Rb have similar transition energies beyond a rotational frequency ħω ≈ 0.55 MeV. This is the only known example of identical bands in nuclei differing by two quasiparticles, in this mass region.