Angular velocity expansions of nuclear rotational energies

Abstract A phenomenological expansion of nuclear rotational energies terms of the angular velocity is discussed and applied to the doubly even nucleaides in the massregon between Ce and Pt. The results of fits with two, three and four parameters are presented. The two-parameter angular velocity expansion is equivalent to the VMI (variable moment of inertia) model and gives a remarkably improved description of rotational to e.g., expansions in terms of I ( I + 1). An increase in the number of parameters from two to three has a relatively small influence on the quality of the fits. However, noticeable improvementis obtained for the good rotors after introduction of the fourth parameter. In these, fits, thethird and the fourth parameter are with exceptions always negative and positive, respectively. The absolute magnitude of the expansion coefficients exhibit severall correlations. The rotational spectra of many doubly even nucleaides have been measured in connection with the present investigation.