Diffusion on surfaces using laser diffraction: Effect of adsorbate lateral interactions

The importance of lateral interactions in surface diffusion is discussed by means of optical second harmonic diffraction from a monolayer grating using model simulations. Measurements of high order diffraction signals during surface diffusion at various laser powers and initial surface coverages provide information on the type of interactions between adsorbates on the surface, i.e. attractive, repulsive, or none. Strong interactions between surface adsorbates are predicted to show unusual behavior of the higher order (n> 1) diffraction signals, with the signal strength sometimes oscillating during diffusion. These results are applicable for linear diffraction as well.