Infrared spectroscopic study of water coadsorbed with Na on the Ru(0 0 1) surface

The coadsorption of a water molecule with Na atoms on the Ru(0 0 1) surface has been studied by infrared reflection absorption spectroscopy. Five different kinds of hydration water monomers were observed on Ru(0 0 1) over a wide coverage range of Na. At a low Na coverage, one of the hydrogen atoms was found to point toward and the other away from the surface. When the Na coverage increased to above 0.06 ML, both hydrogen atoms rotated to face the surface (oxygen-up orientation). The monomer water molecules coadsorbed with Na were found to remain stable without decomposition on a Ru(0 0 1) surface over a wide temperature range at 20–220 K.