Quasideuterons in Light Nuclei

The role of pairing correlations for nucleon pairs with isospin $T=1$ and $T=0$ is investigated for nuclei in the mass region $12 \leq A \leq 42$. For that purpose the two-nucleon densities resulting from nuclear shell-model calculations in one and two major shells are analyzed. 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 and is relevant also for excitations across shell-closures. This robustness also explains why $T=0$ pairing does not lead to such a clear evidence in comparing energies of neighbored nuclei as the "odd-even mass staggering" due to the formation of $T=1$ pairing.