Differential cross section for the 16O(t, p)18O reaction and determination of the size of the two-neutron periphery in the 18O nucleus

Within the theoretical formalism that combines a four-body problem with themultiparticle shell model, it is shown that the cross section for the dineuteron-stripping mechanism is consistent with the experimental angular distribution of protons from the O-16(t, p)O-18 reaction. This makes it possible to find the wave function for the relative motion of the dineutron and O-16 and to obtain thereby the probability density W(r) for the dineutron in O-18, the nn-O-16 interaction potential, and the root-mean-square distance aOE (c) L > (nn) between the dineutron and O-16. The respective calculations reveal that, at r ae 8 fm, the dineutron probability density and a rather deep nn-O-16 potential become negligible, which leads to the absence of a dineuntron periphery in O-18. It seems that one can explain this fact by a rather large value (12.19 MeV) of the dineutron binding energy in this nucleus. Thus, the O-18 nucleus is quite compact an object, despite the excess of two neutrons, and has a neutron skin rather than a periphery.