VIBRATIONAL SIGNATURES OF THE HYDROGEN-WATER INTERACTIONS ON CU(110) AT 100-K AND 300-K

The interaction of water with preadsorbed hydrogen on Cu{110} has been studied by HREELS, TDS, LEED and DELTA-empty set measurements, at temperatures of 100 K and 300 K. The (1x3) reconstructed surface, induced by hydrogen adsorption at 100 K, gives rise to substantial modifications of the vibrational properties and the thermal desorption behaviour of water. In particular, it has been found that the H2O molecules interacting with the adsorbed hydrogen assume an orientation parallel to the copper surface. In contrast, hydrogen adsorbed at 300 K which causes a (1x2) reconstruction does not interact significantly with coadsorbed water and merely blocks adsorption sites in the first monolayer. No evidence for the formation of (H3O+)ad, recently proposed as a reaction product of this coadsorption system on Pt{111}, has been found on Cu{110} at 100 K or 300 K.