Description of negative-parity states in 158Dy and 168Er in the framework of the random phase approximation based on the cranking model

The random phase approximation based on the cranking model is used to study the characteristics of low-lying states with negative parity in 158Dy and 168Er. The connection of the ghost unphysical states of the nucleus (associated with the motion of the center of mass of the nucleus) with the solutions of the equations of motion in the framework of the random phase approximation is clarified. Calculated energy levels and probabilities of E1 transitions are compared with the experimental values. The dependence of the strength constants of the residual interactions and the effective mass of the nucleus on the angular momentum is studied. The model used gives a good qualitative reproduction of the experimental data on levels with negative parity up to about 2 MeV