BAND MIXING IN DOUBLY-EVEN NUCLEI AT THE BEGINNING OF THE RARE-EARTH REGION

A phenomenological three-band model is applied to the four nuclei 152,154Sm and 154,156Gd. The moments of inertia, the intrinsic energies and the intrinsic matrix elements are regarded as free parameters to be determined by a least-squares search on the experimental data. It turns out that the coupling of two Kpi=0+ and one Kpi=2+ bands is adequate to reproduce with great accuracy a large number of experimental data. However, a three-band mixing model does not give a satisfactory description of the backbending effect observed in 154Gd, irrespective of the nature of the third band (K pi=2+ or Kpi=1+). This indicates that backbending may result from a more complex band-mixing mechanism.