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

Abstract

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 ¹⁶O(t, p)¹⁸O reaction. This makes it possible to find the wave function for the relative motion of the dineutron and ¹⁶O and to obtain thereby the probability density W(r) for the dineutron in ¹⁸O, the nn–¹⁶O interaction potential, and the root-mean-square distance 〈L〉_nn between the dineutron and ¹⁶O. The respective calculations reveal that, at r ≈ 8 fm, the dineutron probability density and a rather deep nn–¹⁶O potential become negligible, which leads to the absence of a dineuntron periphery in ¹⁸O. 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 ¹⁸O nucleus is quite compact an object, despite the excess of two neutrons, and has a neutron skin rather than a periphery.