Negative parity bands in even–even isotopes of Ra, Th, U and Pu

Abstract

There are negative parity bands, conveniently labelled Kπ = 0−, 1− and 2−, with very similar patterns of excitation energies in many of the even–even isotopes of Ra, Th, U and Pu. Furthermore, the 3− states in many of these bands decay to the 0+ ground state with reduced B(E3) transition strengths closely similar to one another and comparable to the strengths found in the isotopes of Pb. We propose a Pb core plus exotic cluster model explanation of these observations. Such a treatment accounts for the persistence of these features across many isotopes and gives a good description of the excitation energies and E3 rates for all of them. The wavefunctions generated are intermediate between the weak and strong coupling limits. They suggest that the Kπ = 1− bands consist of doublets, possibly inverted, and thereby give rise to a novel proposal for a unification of some of the disparate band structures seen in 238U.