Electronic effects in SERS by liquid water

By exploiting the attenuated total reflection (ATR)-Otto configuration, surface-enhanced Raman scattering of water at monocrystalline copper and silver electrodes in 0.1 mNa(2)SO(4) was observed at cathodic electrode potentials with hydrogen evolution at a laser wavelength of 647.1 nm. The proposed enhancement model is based on the condition that the upshift of the Fermi level of the electrode and the absorption of one laser photon allow an electron of the electrode at the Fermi level to reach the lower level of the energy band of delocalized electrons in liquid water. The electron interaction with the water molecules in the first hydration shell of cations in the Helmholtz plane is so-called impulse scattering which is the short-time, non-resonant excursion to the anionic ground state of molecules known for a long time in low-energy electron scattering from free molecules. Copyright (c) 2005 John Wiley & Sons, Ltd.