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

摘要

There are negative parity bands, conveniently labelled K-pi = 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 K-pi = 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 U-238.