High-spin structure of the neutron-rich ₄₄^104,106,108 Ru isotopes: γ-vibrational bands and two-quasiparticle excitations

The Ru-104,Ru-106,Ru-108 nuclei have been produced as fission fragments following the fusion reaction Si-28 + Yb-176 at 145 MeV bombarding energy; prompt gamma rays emitted in the reaction were detected using the Eurogam II array. Their high-spin level schemes have been obtained, particularly several side bands have been extended or newly observed. Experimental results are discussed in the framework of both collective model and the rotating mean-field approach in which the Gogny force is the sole input. These calculations provide very good descriptions of both low-spin and high-spin structures observed in the neutron-rich even-A Ru isotopes.