ON THE INFLUENCE OF STEPS ON THE ROTATIONAL ANISOTROPY OF THE 2ND-HARMONIC GENERATION FROM AG ELECTRODES

The second harmonic generation (SHG) from stepped Ag(111) based surfac es in an electrolyte solution have been measured and analyzed. The rot ational anisotropies from these surfaces show a pronounced effect due to the lowering of the surface symmetry relative to a (111) surface. T he results from the stepped surfaces are interpreted in terms of a pse udo mirror plane. The SH response has also been measured during the un derpotential deposition (UPD) of lead onto the stepped crystals and th e results are compared to the well known Ag(111)/Pb2+ system. The SH r esponse during adsorption on defect and terrace sites on Ag(111) are m onitored separately and the contribution from the steps to the SH anis otropy is discussed.