IN-SITU SHG STUDIES OF ADSORPTION INDUCED SURFACE RECONSTRUCTION OF AU(111) ELECTRODES

In situ SHG (Second Harmonic Generation) has been applied to investiga te the axial symmetries of an Au(111)-electrode inserted in various el ectrolytes. Evidence is given for two distinct one-fold axial symmetri es present in different potential ranges. The first can be associated with the well known Au(111)-(root 3 x 23) reconstruction, the second a xial symmetry is of unknown origin, but adsorption induced. Whereas th e first type is lifted upon adsorption (of oxide, hydroxide, sulphate or bromide ions), the second type is formed in adsorbate dependent pot ential ranges. The analysis of the anisotropy data also yielded a gene ral linear dependence of the isotropic amplitude (real part) on the ch arge density.