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Abstract:
The formation and develpment of spatio-temporal concentration patterns associated with the catalytic oxidation of carbon monoxide on a Pt(100) surface modified by deposition of sub monolayers of Au was investigated by means of photoemission electron microscopy (PEEM). The presence of Au atoms essentially reduces the adsorption probability for oxygen and the diffusion coefficient for chemisorbed CO, leading to alterations of the velocities for propagation of O- and CO-waves. At the boundaries between domains of differing Au content, phenomena of refraction and reflection occurred. The refraction obeys Snell's law, while total reflection as found in optics does not occur for chemical waves at less than the critical angle. The observed effects as well as characteristic differences to the previously studied Pt(110) surfaces were explained qualitatively on the basis of the elementary steps involved.
