Effect of Adsorbed Surface Layers on Second-Harmonic Light from Silver

Abstract
It has been found that atomically clean silver surfaces generate approximately four times as much harmonic light as those subjected to adsorption. Existing theories of the nonlinear optics of metals, which are based on bulk properties, must therefore be modified to account for the surface contribution. It is hypothesized that an electric dipole contribution to the nonlinear polarization may account for the present result.