Elastic two-neutron transfer reactions of {sup 58}Ni+{sup 60}Ni and {sup 62}Ni+{sup 64}Ni around the Coulomb barrier

We have measured elastic scattering angular distributions for {sup 58}Ni+{sup 60}Ni at E{sub {sup 58}Ni} =204, 220, 236, and 250 MeV and for {sup 62}Ni+{sup 64}Ni at E{sub {sup 64}Ni} =250 MeV. The measured angular distributions show bell-shaped structures at backward angles for both systems at E{sub lab}=250 MeV which are due to the neutron pair exchange between identical cores for the projectile and target. The pair exchange has been analyzed by using the macroscopic form factor. For elastic scattering the coupled-channels analyses have been performed. The data are reproduced well. The possibility of a nuclear Josephson effect is discussed. {copyright} {ital 1997} {ital The American Physical Society}