Selection rules for surface Raman spectroscopy: Experimental results

Abstract

We report the results of an experimental survey determining the contributing factors for Raman spectral activity of molecules adsorbed on metal surfaces. The systems investigated are benzene, pyrazine, and s-triazine physically adsorbed onto the (111) and (110) faces of single crystal silver. We consider the relative importance of three factors: symmetry reduction, image dipoles (metal optics), and quadrupole polarizability contributions. The experimental data may be explained satisfactorily by involving both the adsite geometry and image effects in the theoretical selection rules. Quadrupole interactions appear neither necessary nor sufficient to predict the proper surface spectra.