The initial growth of water molecules to form the first bilayer and then ice layers on Ru(001) was studied utilizing work function change (ΔΦ), temperature programmed desorption (TPD), and supersonic atomic beam−collision-induced desorption (CID) measurements. A kinetic model that reproduces the first bilayer growth, as determined by the ΔΦ measurements, was developed. It indicates that monomers dominate the cluster size distribution at low coverages, but at high coverages, tetramers gradually become the dominant clusters. Small contributions to ΔΦ suggest that tetramers are cyclic at the adsorbed state with inclined dipoles. CID measurements of H2O and D2O at coverages near one bilayer reveal strong selectivity to the removal of molecules in the A2 adsorption sites over those in the icelike C sites and the A1 sites. Soft removal rates of thicker ice layers as a result of CID with energetic Kripton atoms were then studied as a function of the ice layer thickness. Near the completion of the third bilayer, a sharp stabilization of the ice structure occurs, which leads to two concomitant effects:  (a) a significant decrease in the CID removal rate of the ice layers, and (b) caging of adsorbed nitrogen followed by an extremely sharp desorption of the trapped molecules near 165 K. This happens at the onset of the ice desorption temperature. These effects are discussed in terms of the structure of the first layers of ice which grow on the surface of a Ru(001) single crystal and are consistent with recent model molecular dynamics simulations of such a system.

Work function change (∆Φ) measurements during adsorption and surface heating in a ∆Φ-temperature programmed reaction (TPR) mode combined with TPD are demonstrated to provide new information on the interaction and chemistry of ethylene on Ru(001). Rearrangement of second layer ethylene molecules has been observed between 82 and 120 K. This is a competing process with molecular desorption, interpreted as a result of migration of second layer molecules toward the surface. Our results are consistent with and support previous studies that suggested the formation of a surface intermediate (η 2 (C,C)CHCH 2 ) during ethylene dehydrogenation to ethylidine. Employing a derivative mode with respect to temperature -d(∆Φ)/dT, we find an early onset for ethylidine decomposition near 265 K. ∆Φ-TPR measurements in the range 560-720 K reveal three distinct CH decomposition peaks, reflecting different activation energies for the decomposition reaction sites. The dipole moment of an adsorbed CH has been determined to be µ ) 0.43 D, suggesting a rather polarized Ru-CH complex; its structure is independent of the adsorption site. Finally, carbide polymerization to form graphite has been detected above T s ) 560 K for the first time using work function change measurements. Good agreement was found between the contribution to ∆Φ by the graphite layer formed on the Ru(001) surface and ab initio calculations performed previously on this system.

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