Anisotropic chemical waves on a stepped surface: the NO+H 2 and O 2+H 2 reactions on Rh(533)

Abstract

The adsorption of oxygen and chemical wave patterns in the O 2+H 2 and NO+H 2 reactions have been studied at p<10 −4 mbar on an Rh(533) surface. Low energy electron diffraction, Auger electron spectroscopy, thermal desorption spectroscopy and work function measurements with a Kelvin probe served to characterize the integral adsorption behavior, whereas photoemission electron microscopy was used as the spatially resolving method. Oxygen adsorbs on Rh(533) with an initial sticking coefficient of 0.8 at 340 K. Reaction fronts elliptically deformed in the direction parallel to the step edges were found in the bistable O 2+H 2 reaction. Similarly, also in the excitable NO+H 2 reaction elliptically deformed target patterns and spiral waves were observed in the temperature range from 430 to 490 K. For both reactions the dependence of the front/pulse velocity on temperature and p H 2 was investigated in the direction parallel and perpendicular to the step edges.