Abstract
The desorption kinetics of H 2O and D 2O were studied on a flat Ru(0001) and a stepped Ru(101̄8) surface by TDS, Δø measurements (120 to 300 K) and LEED. In accordance with other authors we observed three typical desorption peaks for H 2O on Ru(0001) (C, 155 K; A 2, 190 K; and A 1, 212 K), and the respective peaks for the isotope effect for D 2O on Ru(0001), characterized by a missing A 1 peak. Isothermal Δø measurements were performed in order to determine the different desorption kinetics for H 2O and D 2O. Neither for D 2O nor for H 2O the desorption of the A 2 state can be described by first order kinetics. Especially for the A 2 peak of H 2O, we observed an initial range of first order kinetics followed by a strong deviation, which could be described by Avrami kinetics or lateral interactions. Also, Δø measurements during desorption give evidence for a complicated adsorption kinetic process. In order to modify the water bilayer structure, a stepped Ru(101̄8) surface was used for comparison. These measurements are in progress and should give further information about the isotope effect.
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