Rotations of Nuclei with Octupole Deformations

We study collective interactions capable to generate rotations in nuclei with a simultaneous presence of octupole and quadrupole deformations. On this basis we propose a collective Hamiltonian which incorporates the standard quadrupole terms, octupole terms classified according to the irreducible representations of the octahedron point symmetry group, a quadrupole-octupole interaction, as well as a term for the band-head energy linear in K (the projection of angular momentum on the body-fixed z-axis). The energy is subsequently minimised with respect to K for each given value of the angular momentum I, resulting in K values increasing with I within each band. We demonstrate that this Hamiltonian is able to reproduce a variety of 'beat' patterns observed recently for the odd-even staggering in octupole bands of light actinides. In addition, we suppose that the model can be applied to reproduce the staggering effects in rotational negative parity bands built on octupole vibrations. On the above basis we expect that the interactions involved would provide a relevant handle in the study of collective phenomena in nuclei and other quantum mechanical systems with a presence of octupole degrees of freedom. (authors)