High-spin structures of 88Kr and 89Rb: Evolution from collective to single-particle behaviors

The high-spin states of the two neutron-rich nuclei Kr-88(52) and Rb-89(52) have been studied from the O-18 + Pb-208 fusion-fission reaction. Their level schemes were built from triple gamma-ray coincidence data, and gamma-gamma angular correlations were analyzed in order to assign spin and parity values to most of the observed states. The two level schemes evolve from collective structures to single-particle excitations as a function of the excitation energy. Comparison with results of shell-model calculations gives the specific proton and neutron configurations which are involved to generate the angular momentum along the yrast lines.