[en] One- and two-charge-transfer reactions were studied in the ¹²C+¹⁹⁷Au and ¹⁶O+¹⁹⁷Au systems at bombarding energies around the Coulomb barrier. Transfer probabilities for the same Coulomb reduced radius, extracted from angular distribution measurements, show a strong dependence on the bombarding energy and are interpreted within a semiclassical model. Quasielastic scattering data are analyzed in terms of an energy-dependent optical model. copyright 1996 The American Physical Society