[en] Measurements of quasi-elastic reactions occuring during collisions of low-energy ⁵⁸Ni ions with isotopes of tin and samarium have been made, using a recoil separator. Exicitation functions of integrated fields of one- and two-nucleon transfer on even tin isotopes (A=116 to 124) taken over the c.m. energy range 125 to 150 MeV are well described in terms of both DWBA and semi-classical models of the transfer process. Simple coupled-channels calculations show that both inelastic scattering and transfer coupling is predicted to give rise to an isotopic effect, inelastig coupling should not. In contrast to the tin results, measurements taken on samarium isotopes (A=144 to 154) vary in an unexpected way. The energy dependence of one neutron transfer on the heavier isotopes, is more gradual than for ¹⁴⁴Sm. They also are less than predictions based on either DWBA or a semi-classical model. Preliminary particle-gamma coincidence measurements show evidence for an appreciable amount of nucleon transfer proceding via target excitation. 10 figs., 2 tabs., 14 refs