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The First Layers of Water on Ru(001) Y. Lilach, L. Romm, T. Livneh, and M. Asscher*

Summary: The First Layers of Water on Ru(001)
Y. Lilach, L. Romm, T. Livneh, and M. Asscher*
Department of Physical Chemistry and the Farkas Center for Light Induced Processes, The Hebrew UniVersity,
Jerusalem 91904, Israel
ReceiVed: September 27, 2000; In Final Form: January 16, 2001
The initial growth of water molecules to form the first bilayer and then ice layers on Ru(001) was studied
utilizing work function change (), 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 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 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.


Source: Asscher, Micha - Institute of Chemistry, Hebrew University of Jerusalem


Collections: Chemistry