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

Abstract In this paper, odd-A nuclei in the vibrational to γ-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 β-part potential for the even-even core coupled with a single nucleon in a j = 3 / 2 orbit via the β-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 187,189,191,193,195Ir. It is clearly shown from both the level energies and the known B(E2) values for 191,193Ir fitted that the model with the β-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.