Surface-Enchanced Raman Scattering from Pyridine on Ag(111)

This Letter reports the first ultrahigh-vacuum study of surface-enhanced Raman scattering from pyridine adsorbed on a clean single-crystal silver surface containing a smooth modulation (1 periodicity) to allow optical coupling to surface plasmon polaritons. A large mode-selective enhancement (10^4) of the Raman signal from the first monolayer is observed at surface-plasmon-polariton resonance. Coverages greater than one monolayer show a smaller enhancement (10^2).