High Spin Band Structure in ¹¹²Ru

Levels in the neutron-rich ¹¹²Ru nucleus have been investigated by observing prompt gamma-rays from the spontaneous fission of ²⁵²Cf with the Gammasphere detector array. The ground-state band and the one-phonon g-vibrational band have been confirmed and extended with spin up to 16ħ and 15ħ, respectively. The other two side bands, one proposed as two-phonon g-vibrational band and the other proposed as two-quasiparticle band, have been observed for the first time. The total-Routhian-surface calculations show that rotational ¹¹²Ru nucleus has triaxial deformation with parameters β₂～0.27 and γ=-29 °. 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 quasiparticle band has also been discussed.