NEGATIVE-PARITY STATES OF N=88 ISOTONES IN THE SDF BOSON PLUS A FERMION PAIR MODEL

Abstract

The energy levels of negative parity states of N = 88 isotones: Yb-158, Er-156 and Dy-154 are studied in terms of the SDF interacting boson approximation (IBA) model with one s- or d-boson being able to break and form a fermion pair. The fermion pair is allowed to occupy the iota-13/2 single particle orbit. It is found that the energy levels of the negative parity bands of these nuclei can be reproduced satisfactorily. The backbends of the moment of inertia can be also reasonably described.