SCATTERING-ANGLE DEPENDENCE OF THE RAMAN INTENSITY OF PYRIDINE MOLECULES ADSORBED ON ROUGH SILVER ELECTRODES

We have measured the scattering-angle dependence of the Raman intensit y of the ring breathing mode (1005 cm-1) of pyridine molecules adsorbe d on silver electrodes with rough surfaces. For both large and small s urface roughness (rms amplitude approximately 2500 and approximately 9 0 angstrom, respectively), the Raman intensity decreases monotonically with increasing scattering angles measured from the surface normal. T he depolarization ratio shows weak angular dependence within the range between 0.5 and 1.3. The observed angular dependence and depolarizati on ratio of Raman intensity cannot be explained by the electromagnetic theory that treats interface roughness as a perturbation. Thus we hav e adopted an effective dielectric-layer model to obtain a better agree ment with the experimental data. In this model the scattering dipoles are embedded in an effective dielectric layer formed by oxidation-redu ction cycles of the electrode surface.