Collective Band Structures in Neutron-Rich ¹⁰⁸Mo Nucleus

High spin states in the neutron-rich ¹⁰⁸Mo nucleus are studied by measuring prompt γ-rays following the spontaneous fission of ²⁵²Cf with a Gammasphere detector array. The ground-state band is confirmed, and the one-phonon γ-vibrational band is updated with spin up to 12ħ. A new collective band with the band head level at 1422.4keV is suggested as a two-phonon γ-vibrational band. Another new band is proposed as a two-quasi-proton excitation band. Systematic characteristics of the collective bands are discussed.