ELECTRONIC DISTRIBUTION AND 2ND-HARMONIC GENERATION AT THE METAL-ELECTROLYTE INTERFACE

A model for second-harmonic generation at the metal-solution interface is presented in which the metal is modeled as jellium, and the solution is characterized by its optical dielectric constant. The coefficient a characterizing the nonlinear optical response perpendicular to the surface is calculated both for bare metal electrodes and for metals covered with an overlayer of a different metal. Generally, the presence of the solution reduces the absolute value of a, particularly for negatively charged surfaces, while a metal overlayer enhances it. Our calculations are compared with similar results for metal surfaces in the vacuum, and discussed with respect to experimetal findings.