Short-range (pairing) versus long-range (collective) correlations in two-neutron transfer reactions induced by 18O

It is shown that the pairing correlation is very important for the elastic two-neutron transfer reactions, for reaction induced by 84 MeV 18O on several targets with low collectivity in its ground state (spherical), proceeding through the one-step process. For the transition to lower excited states, the one-step process also dominated, for the final nuclei having low collectivity. On the contrary, if the collectivity of these states is considerable, the two-neutron transfer reaction is dominated by a two-step process through an intermediate partition.