γ-Unstable Bohr Hamiltonian with sextic potential for odd-A nuclei

In this paper, odd-A nuclei in the vibrational to gamma-soft transitional region are studied in the collective model, in which the odd-A system is described by the Bohr Hamiltonian with the quasi exactly solvable sextic beta-part potential for the even-even core coupled with a single nucleon in a j = 3/2 orbit via the beta-independent five-dimensional spin-orbit interaction and the total angular momentum degeneracy breaking term. To test the validity of the coupling scheme, we use the model to reproduce experimentally available level energies and B(E2) values of Ir-187,Ir-189,Ir-191,Ir-193,Ir-195. It is clearly shown from both the level energies and the known B(E2) values for Ir-191,Ir-193 fitted that the model with the beta-independent five-dimensional spin orbit interaction and the total angular momentum degeneracy breaking term seems adequate to describe the low-lying level pattern and the structure of these odd-A nuclei. (C) 2020 Elsevier B.V. All rights reserved.