REORIENTATION OF CHEMISORBED WATER ON NI(110) BY HYDROGEN-BONDING TO 2ND-LAYER

Water chemisorbs molecularly on Ni(110) at 180 K producing a c(2 x 2) overlayer, at 0.5 ML (ML = monolayer = 1.15 x 10(15) molecules cm-2). This water is undetectable by ir methods which indicates the absence of clustering (and, hence, no intermolecular H bonding) in the first 0.5 ML. Population of a second "icelike" layer, which is nearly saturated after an additional 0.5 ML, makes the first 0.5 ML ir active and produces strong H-bonding interactions. The plane of the chemisorbed water, which is originally parallel to the surface, is reoriented towards the surface normal on filling of the second layer.