Angular and velocity distributions of desorbing product carbon dioxide from different reaction sites on stepped platinum (112)

The angular and velocity distributions of desorbing product CO2 were studied in the CO oxidation on a stepped Pt(112)=(s)3(111)x(001) surface by means of angle-resolved thermal desorption combined with a cross-correlation time-of-flight technique. The desorption occurs mainly along the terrace normal, indicating predominant CO2 formation on the terrace. The translational temperature of this CO2 is maximized to 1330 K around the terrace normal. On the other hand, the angular distribution becomes asymmetric at small CO coverages when the desorption angle is varied perpendicularly to the step edges. This indicates a new component collimated at the desorption angle of -25 degrees. It is assigned to the desorption from step sites. The maximum translational temperature of this CO2 is 1190 K. The desorption of CO and oxygen shows a simple cosine distribution, providing no structural information.