Study Shapes and Alignments of Rotational States in Some Rare-Earth Nuclei

Abstract

The ground state rotational band members for the studied nuclei have been identified and their energies calculated to about 0.3%. These energies provide good test of various models for rotational bands, and impressive agreement is observed with a theoretical calculations by the variable moment of inertia (VMI) model and cubic polynomial (CP) formula. In addition to giving an excellent fit to the excitation energy of the ground-band levels in all nuclei. Also reproduces a critical spin Ic beyond which the square rotational frequency ω2 decreases although the moment of inertia ℑ keeps on increasing, thus resulting in back bending in I -ω2 plot for some of the studied nuclei. This feature is predicted to appear not only in the deformed nuclei but also at quite low spins in nearly spherical nuclei as well. Also the formula contains the low and high spin behavior in agreement with the available experimental data.