Abstract
The eveneven rare-earth nuclei in U(5)SU(3) region at neutron number (N) = 90, have been systematically studied using the BohrMottelson Model (BM), Interacting Vector Boson Model (IVBM), and Interacting Boson Model (IBM). The positive ground-state band (GSB) of Sm-152, Gd-154, and Dy-156 nuclei has been calculated by using BM, IVBM, and IBM, while the negative-parity band (NPB) of those nuclei are calculated by BM and IVBM only. To determine the intermediate structure, the ratio (r(I + 2)/I) and E-GOS curve (E-Gamma Over Spin) as a function of the spin (I) have been drawn. In the IBM, the calculated reduced B(E2) transition probabilities of the GSB in the Sm-152, Gd-154, and Dy-156 nuclei are analyzed and compared to the prediction of vibrational U(5) and rotational SU(3) limits. In the SmDy nuclei with N = 90, the U(5)SU(3) IBM potential energy surfaces (PES's) are analyzed and evolve from spherical to deformed shapes with increasing the boson number. The critical phase transition points are identified in the space of model parameters and Sm-152,Gd-154, and Dy-156 nuclei have been found to be close to critical points.