Surface enhanced Raman scattering (SERS) from pyridine on silver-UHV interfaces: Excitation spectra

Abstract

Excitation spectra of various surface enhanced Raman lines of pyridine adsorbed to evaporated silver films (1 L exposure) in UHV have been measured. Relative to ordinary scattering from thick pyridine layers on SERS inactive Ag films, every vibration exhibits a resonance profile which peaks at the same Stokes frequency corresponding to 2.0 eV independent of vibration. This value is shifted to the red after additional adsorption of 10³ L of pyridine on the SERS active film. The ratio of corresponding Raman line intensities from ’’bulk’’ and ’’surface’’ pyridine varies differently for different vibrations with exciting frequency. The results are discussed with respect to various proposed enhancement mechanisms.