Reorientation of chemisorbed water on Ni(110) by hydrogen bonding to second layer

Water chemisorbs molecularly on Ni(110) at 180 K producing a c(2×2) overlayer, at 0.5 ML (ML=monolayer=1.15×${10}^{15}$ molecules ${\mathrm{cm}}^{\mathrm{-}2}$). 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.