Energy differences of ground state and γ1 bands as a hallmark of collective behavior

Abstract

The systematics of experimental energy differences between the levels of the ground state band and the even levels of the γ1 band in even-even nuclei are studied as a function of the angular momentum L. Three clearly different trends are seen. In deformed nuclei a decrease of the energy differences with increasing L is found. In γ-unstable and triaxial nuclei the energy differences are increasing with increasing L, but the rate of increase is larger in the triaxial case by an order of magnitude in relation to the γ-unstable case. This observation is corroborated by numerical results and analytic expressions in the framework of several special solutions of the Bohr Hamiltonian.