WAVELENGTH-DEPENDENT 2ND HARMONIC-GENERATION FROM AG(111) IN SOLUTION

We examine the optical second harmonic response in the UV, visible, and infrared regions from Ag(111) immersed in aqueous electrolyte. We find that the second harmonic rotational anisotropy, which has been shown to be sensitive to the electrode crystalline structure, shows a marked wavelength dependence which is consistent with the electronic band structure for Ag(111). The anisotropy is highly sensitive to electrochemical potential induced changes in the surface electronic properties when the second harmonic frequency is in the UV region. This is in sharp contrast to the potential dependence of the second harmonic response in the visible or infrared region which arises entirely from the isotropic susceptibility elements.