ABSTRACT
Interfacial second harmonic generation (SHG) is an optical spectroscopy that is inherently surface sensitive. All effects that modify the electron density profile of the interface are mapped into the SHG process. Therefore, SHG depends on the exciting and SH frequency, on the surface structure, and on adsorbates and adlayers. For metal electrodes there is a remarkable dependence of SHG on potential, adsorption, and charge density at the metal and surface structure. Using the advanced form of the SHG anisotropy, the interference SHG anisotropy, one can determine the anisotropy of the SH field itself and can pursue how the various isotropic and anisotropic sources contributing to this field evolve with potential and adsorption. This yields information on the geometric and electronic structure of the interface and adlayer to unparalleled details.
