Analysis of the negative-parity yrast band in 155Tb

摘要

Using the particle-rotor model, the energy spectrum and the B(M1)/B(E2) ratio of the negative-parity yrast band in 155Tb are investigated and compared with the experimental data before and after the band-crossing. It is noted that before and after the band-crossing the moment of inertia of the core is a smooth function of the total angular momentum I and can be described by the ab formula. The yrast band of 155Tb with negative parity may be triaxially deformed (γ=-13°) before and an axially symmetric shape (γ=0°) after the band-crossing.