Anomalies in the experimental spectra for the positive-parity states of the Pt and Hg isotopes are explained in the $\gamma$-deformed-rotor model which takes into account the coupling of the two quasiparticle excitations with the ground band. It is found that the 0-2-quasiparticle coupling is very important. Moreover, it is recognized that the linear increase in the moment of inertia with the square of the angular velocity can be described by this coupling.

• Received 24 June 1977

DOI:https://doi.org/10.1103/PhysRevLett.39.1128