Chemical effects in surface-enhanced raman scattering: pyridine chemisorbed on silver adatoms on Rh (100)

Surface-enhanced Raman scattering (SERS) has been observed from pyridine chemisorbed on silver adatoms which had been deposited at submonolayer coverage on a Rh (100) substrate under ultrahigh vacuum. The vibrational frequencies measured are characteristic of pyridine chemically adsorbed on the silver adatoms and an enhancement factor of ≈ 15–65 is calculated from the intensity of the scattering. This enhancement factor is in addition to the factor of four electromagnetic enhancement found for flat metal surfaces and therefore provides unambiguous evidence for the existence and magnitude of chemical enhancement in SERS.