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We report on the first experiments showing the influence of surface magnetization on optical second harmonic generation in reflection at a Fe(llO) surface. The magneto-optical Kerr effect modifies the hyperpolarizability of the surface in the optical field, leading to a dependence of the second harmonic yield on the direction of magnetization relative to the light fields. For the clean surface an effect of 25% was determined, which decays exponentially with surface contamination by the residual gas, thus demonstrating the high surface sensitivity of this technique.

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The adsorption dynamics of water on NaCl(100) is studied by molecular dynamics calculations as a function of coverage. We find that, starting from a critical coverage of about 1/2 monolayer, a coupling of the water dipoles sets in and the interaction between the water molecules wins over the interaction between adsorbate and substrate leading via percolation to formation of infinite cluster networks. This effect is confirmed qualitatively by surface sensitive optical second harmonic measurements with well-controlled water exposure. At a coverage of one bilayer, a two-dimensional ‘‘ice’’ structure is found to be stable. Simulated low-energy electron diffraction (LEED) patterns for this configuration are in excellent agreement with recent observation of a c(4×2) overstructure.