Resonance Raman Scattering by Molecules Adsorbed on Smooth Metal Surfaces.

In this thesis we explore the use of Raman scattering as a surface-sensitive spectroscopic probe to obtain information about the valence electron excitations of the adsorbate -substrate complexes. Measurement of the excitation profiles of the Raman scattering by the various vibration modes is in fact a form of modulation spectroscopy. The resonances in the excitation-profile spectra for the various vibration modes of different symmetry can give information not only about the energies, widths and strengths of the valence electron excitations, but also about the underlying Raman scattering mechanisms and the vibronic character of the electron states involved in the RS process. By using a smooth surface one can also make use of polarization selection rules to determine the site symmetries of the adsorbed molecules and the non-zero components of the Raman tensor arising from different electronic excitations. The measurement of polarization resolved Raman scattering excitation-profile spectra of crystal violet adsorbed on smooth noble metal surfaces is an example.