Low-lying bands as alpha-like dipole excitations of a coherent quadrupole boson state

Abstract

A phenomenological analysis of low-lying positive and negative-parity bands of some heavy deformed nuclei is carried out within a coherent-state model by making use of an interacting boson Hamiltonian where quadrupole bosons associated to the nucleon motion are coupled to scalar and dipole bosons introduced to describe the motion of α-clusters with respect to a deformed nuclear core. The deformation is induced by the use of an intrinsic ground state which is coherent in the quadrupole bosons only. The physical states are generated through angular-momentum projection from intrinsic wavefunctions obtained by the action of dipole operators of the simplest form on the coherent intrinsic ground state. Energy spectra and electromagnetic transition probabilities are calculated and compared to experiments. The good overall agreement between predictions and experiments is in support of the important role played by α-clustering in deformed heavy nuclei.