Classification of beta- and gamma-ray transitions between intrinsic states in deformed even-mass nuclei

Abstract

The description of intrinsic states of deformed even-mass nuclei by the product wave functions of the strong coupling model, using Nilsson wave functions to describe the intrinsic particle configurations, is shown to lead to selection rules which depend on the coupling between the last two particles. In the case in which the coupling in the final and initial states is the same, the description leads, in the asymptotic limit of the Nilsson wave functions, to selection rules similar to those proposed earlier for odd-mass nuclei. For nuclear states with different relative couplings the selection rules lead most frequently to K-forbiddenness. It is shown that, if the non-transforming particle in the two-particle product wave function is not the same in the final and initial states, the resulting two-particle transition is formally forbidden. The experimental transition rates in even-mass nuclei to which definite configurations can be assigned are observed to fall within well-defined ranges characteristic of the degree of forbiddenness predicted by the selection rules. Furthermore, the data on log ft-values indicate that single-particle transitions occur with essentially the same speed whether the transforming particle is in an odd-mass or an even-mass nucleus.