Pairing model for Pr-isotopes

Abstract

The interaction between neutrons and protons filling different major shells is treated as a perturbation within the framework of the pairing force model. The lowest order effect is to keep the pairing model equations unchanged; only the single nucleon energies to be used therein are modified by an amount dependent on the number of the opposite kind of nucleons and the zero-rank component of the n-p potential. This effect produces the observed ground-state spins of Pr^{141, 143, 145}. The quasi-neutron-quasi-proton interaction, which contains the effect from the higher multipole components of the n-p potential, must be diagonalised to attempt a detailed fit to the spectra. This is particularly true for the odd nuclei Pr^{142, 143}. There are two competing configurations for the ground state of Pr¹⁴⁴, a diagnolisation between which is now in progress.