Collective Band Structures and Identification of One-Phonon and Two-Phonon γ-Vibrational Bands in 109Tc

The high spin states of the neutron-rich ¹⁰⁹Tc nucleus are reinvestigated by observing prompt γ-rays from the spontaneous fission of ²⁵²Cf. The previously known yrast band based on the 7/2⁺ state is updated. A side band built on the 11/2⁺ state is expanded and a new band based on the 15/2⁺ state is identified. Band crossing in the yrast band occurs around ≈0.36 MeV. This band crossing is associated with the alignment of two h_11/2 neutrons according to the cranked shell model calculations. The band based on the 11/2⁺ state is proposed as a candidate for the one-phonon γ-vibrational band, and the band built on the 15/2⁺ state is proposed as a candidate for the two-phonon γ-vibrational band. Other characteristics for the observed bands are discussed.