Photo-electron emission microscopy was used to study the influence of a noisy reactant gas flux composition upon spatio-temporal pattern development in the CO oxidation reaction on stepped Ir(977) surfaces. The anisotropic diffusion of CO, parallel and normal to the steps, produced elliptic shapes for large O islands at small noise amplitudes. The long axes of the ellipses were aligned along the steps. At increased noise amplitudes, the density of O island ellipses became larger while maintaining their alignment. Two-dimensioal modeling of the phenomena, based upon reaction-diffusion differential equations, quite closely reproduced the experimental findings.

The Consequences of Anisotropic Diffusion and Noise: PEEM at the CO Oxidation Reaction on Stepped Ir(111) Surfaces. S.Wehner, P.Hoffmann, D.Schmeisser, H.R.Brand, J.Küppers: Chemical Physics Letters, 2006, 423[1-3], 39-44