ELASTIC 2-NEUTRON TRANSFER-REACTIONS OF NI-58-60 AND NI-62+NI-64 AROUND THE COULOMB BARRIER(NI)

We have measured elastic scattering for Ni-58 + Ni-60, Ni-58 + Ni-64 a nd Ni-62 + Ni-64 systems at several incident energies and two-neutron transfer reaction for the Ni-58 + Ni-64 system at E-cm = 118.8 MeV. We have observed the elastic two-neutron transfer reactions for heavier systems of Ni-58 + Ni-60, and Ni-62 + Ni-64 at E-cm = 127.1 and 123.0 MeV, respectively, for the first time. Their angular distributions hav e shown the bell-shaped structures at backward angles which are due to the neutron-pair exchange between the identical cores for the project ile and target. We have obtained the optical potential parameters thro ugh the coupled-channels analyses for elastic scattering. The pair-tra nsfer cross section has been analysed by using the macroscopic form fa ctor. The pair-deformation parameter beta(p), which measures the colle ctive character of the pair-transfer mode, has become larger as the nu mber of valence neutrons increase. The possibility of a nuclear Joseph son effect is discussed.