The variable moment-of-inertia (VMI) model for the asymmetric shape of nuclei which allows a simultaneous analysis of the data for both the ground-state band and the $\gamma$-vibrational band in even-even nuclei is worked out. For the asymmetric rotor we use Krutov's model which is based on the assumption of rotational flow and a rotationally invariant core in nuclei and predicts a linear dependence of the moment of inertia on the deformation-a condition used by the VMI model. The calculations (using a least-squares-fitting procedure) are carried out for all the even-even nuclei which have at least two states above the ground state and two states above the $\gamma$-vibrational band head well established. The over-all comparison with the experimental data is very good. The fits to the ground-state band, however, remain essentially the same as for the VMI model.

• Received 31 August 1972

DOI:https://doi.org/10.1103/PhysRevC.7.2476