We study the even-even U and Pu nuclei in the framework of the $\mathrm{spdf}$ interacting boson model. Analysis of the systematics of positive and negative parity bands, together with the $E1,$ $E2,$ and $E3\mathrm{}$ transitions, suggests that the properties of low-lying states can be understood without the introduction of stable octupole deformation. Double octupole phonon characteristics are also identified in certain low-lying $0^{+}$ excited states in U and Pu.

• Received 11 September 2002

DOI:https://doi.org/10.1103/PhysRevC.67.014305