Study of Er Isotopes in IBA-plus-Two-Fermion-Pairs Model

Abstract

The high-spin states up to the vicinity of the second backbends of the Er isotopes are studied in the IBA-plus-two-fermion-pairs model. It was found that the energy levels of the quasi-β, quasi-γ bands as well as the yrast state can be reproduced reasonably well. The second backbends can be interpreted as the band crossings of the two-fermion-pair rotational band with the ground state bands. The B(E2) values were calculated and compared with the available experimental data. The drops of the B(E2) values at the backbends can be reproduced. The calculated moments of inertia and B(E2) values change too sharply as compared with the experimental values. Possible improvements of the model are discussed.