A novel approach to analyze the optical second harmonic generation anisotropy at surfaces employing interference techniques. Example: the Au(110) electrode

Different sets of susceptibility coefficients a, b, c and d can reproduce the same second harmonic generation (SHG) anisotropy curve, but only one set corresponds to the electronic and geometric structure of the sample surface. A new approach, interference SHG anisotropy, is presented which is generally suitable to determine this physically relevant set of coefficients. It is applied to the study of the SHG anisotropy of the Au(110) electrode, which could not be analyzed hitherto. The distinct SHG response upon Br− adsorption indicates corresponding changes of the structural and electronic state of this interface.