Quasi-deuterons in light nuclei

Abstract

The role of pairing correlations for nucleon pairs with isospin T = 1 and T = 0 is investigated for ground-states of nuclei in the mass region 12 ≤ A ≤ 42. For that purpose, the two-nucleon densities resulting from nuclear shell-model calculations in one and two major shells are analyzed. Various tools are applied in this analysis including the sensitivity of correlation effects on components of the NN interaction. Significant effects on the resulting energies are observed due to the formation of T = 0 pairs. The formation of quasi-deuterons is maximal for symmetric nuclei with N = Z. The formation of T = 0 pairs is less sensitive to the density of single-particle states close to the Fermi energy than the T = 1 pairing. Therefore the correlations in T = 0 pairs are relevant also for excitations across shell closures. This robustness also explains why T = 0 pairing does not lead to such clear evidence in comparing energies of neighbored nuclei as the ‘odd–even mass staggering’ due to the formation of T = 1 pairing.