Surface-enhanced Raman scattering from molecules adsorbed on mercury

Raman scattering from pyridine, benzene, or cyclohexane molecules adsorbed on a liquid mercury surface is observed to be strongly enhanced relative to the same molecules in the gas phase or solution. The nominal enhancement factors (estimated for monolayer absorption, as conventional) are of the order of 10⁴ to 10⁶. Previous observations of such strong surface-enhanced Raman scattering have all involved roughened solid metal surfaces; the prevalent view is that surface roughness on the order of a few hundred angstroms is an essential condition. Our results show this does not hold for liquid mercury surfaces.