Intermediate coupling approach in the unified nuclear model: (I). Odd-mass Pm nuclei

Abstract

The properties of the low-lying levels of the odd-mass promethium isotopes are investigated within the framework of the intermediate coupling approach in the unified nuclear model. It is assumed that the last odd proton has available to it the 1 g 7 2 and 2 d 5 s states and is coupled to the collective surface vibrations of the doubly even core of the nucleus. The resulting Hamiltonian of the coupled system is diagonalized including all states with up to three phonons of the quadrupole vibrations. Using reasonable values for the coupling strength and for the “effective” spacing in energy between the g 7 2 and d 5 2 states, the low-lying energy levels, spins and parities of 145Pm, 147Pm and 149Pm are calculated. These are in fairly good agreement with experimental data. The electromagnetic transition probabilities and the nuclear moments are calculated using the wave functions obtained. In cases these results are also in substantial agreement with the experimentally observed values. Finally, the validity of the approximations used in the present analysis and the possible reasons for some of the discrepancies between the theoretical and experimental results are discussed.