a model for the adsorbate-metal surface interaction and a charge transfer mechanism for surface-enhanced Raman scattering (SERS) is presented. An analytical expression has been derived, using the time approach for the Raman scattering, to calculate the SERS intensity vs applied potential profiles and their dependence on the exciting radiation. The analytical expression derived to compute the SERS excitation profiles has been applied for pyridine and for the ion complex [Fe-2(CN)(10)bipy](6-) adsorbed on a silver electrode. Good agreement between calculated and excitation profiles has been obtained for both investigated species. The developed model has also been used to explain some SERS features on electrode surfaces, such as the dependence of the potential of maximum SERS intensity, V-max, on the chemical composition of the supporting electrolyte and the chemical nature of the adsorbate and substrate.