Intrinsic structures and associated rotational bands in deformed even-even nuclei of the actinide region

Abstract

Experimentally observed energy levels of deformed even-even nuclei with Z ≥ 88 and N ≥ 134 are classified in terms of their intrinsic structures and associated rotational bands. Interleaving of the ground-state K π = 0 + band and the first excited K π = 0 − band levels in the beginning of the region is presented as possible evidence for spin evolution of reflection-asymmetric (stable octupole) shapes. Rotational alignment and possible backbending in the ground-state band levels is discussed. Structures connected with one-phonon quadrupole (β and γ) and octupole and two-phonon vibrations are described. Other modes of excitation for 0 + structures, for example, pairing vibrations and α clustering, are pointed out. Available information on the occurrence of collective dipole excitations connected with the “scissors” or “twisting” mode is also included. Bands connected with two-quasiparticle excitations are listed. Evidence for superdeformations and hyperdeformations connected with fission isomers, and related spectroscopies in the second and third well, is presented. Our literature cutoff date is March 1991.