High-Spin Structure in Neutron-Rich ¹⁰⁸Ru Nucleus

High spin states in the neutron-rich ¹⁰⁸Ru nucleus have been studied through measuring prompt γ-ray coincidences following the spontaneous fission of ²⁵²Cf with the Gammasphere detector array. The yrast band has been confirmed. The one-phonon γ-vibrational band and the two-quasiparticle band based on the 5^- level have been extended up to 13⁺ and 15^-, respectively. In addition, two levels at 1644.8keV and 1826.5keV excitation energies are newly identified and proposed to be the members of a two phonon γ-vibrational band. It is shown that the ¹⁰⁸Ru nucleus has triaxial deformation with parameters β₂～0.29 and γ=-22°from the total Routhian surface calculations. The observed band crossing in the yrast band is due to the alignment of a pair of h_11/2 neutrons according to the cranked shell model calculations. The possible configuration for the two-quasiparticle band has been discussed.