WATER AT SURFACES - WHAT CAN WE LEARN FROM VIBRATIONAL SPECTROSCOPY

Recent developments in the vibrational spectroscopy of thin films of w ater adsorbed on well defined metal surfaces under ultra-high vacuum ( UHV) conditions will be discussed. New results will be presented for H 2O and D2O adsorbed on Cu(110), measured using grazing incidence refle ction-absorption infrared spectroscopy (RAIRS). These will be discusse d in context with previous high-resolution electron energy loss spectr oscopy (HREELS) measurements of H2O on Pd(110). Both of these results are typical of measurements from other laboratories. Particular attent ion will be paid to the O-H stretching region of the spectrum. A detai led examination of this region of the spectrum is used to study the am orphous to crystalline phase transition in thin films, the temperature dependence of the sticking coefficient of water, and the structure of the first one or two layers of water directly at the solid interface. The spectroscopic signature observed for very thin films is found to be consistently different from that of crystalline ice, and the possib le reasons for this difference are discussed.