N. A. Mansour
The results from the variable moment of inertia (VMI) and cubic polynomial (CP) models with the available experimental information on transition energies for the yrast band levels in all studied nuclei. These models has been generalized so as to be applicable to transitional and vibrational nuclei by requiring that the extended models reduce at low angular momentum, to the polynomial dependence which gives excellent fits to the experimental spectra in the spherical, transitional and deformed regions. The level structure indicate a transition from collective to few-particle characteristics at high spin, possibly suggesting a change shape from prolate through triaxial to oblate. The loss of collectivity occurs at much lower angular momentum than predicted by calculations. The calculated Qt-value of the yrast band of the nucleus with N = 90.