SYMMETRY OF REACTION SITES AND ANISOTROPY IN ANGULAR AND VELOCITY DISTRIBUTIONS OF DESORBING PRODUCT CARBON-DIOXIDE ON PLATINUM (110)(1X2)

The angular and velocity distributions of reactive CO2 desorption were studied along the narrow terrace of Pt(110)(1 X 2) over a wide range of CO coverage by means of angle-resolved thermal desorption combined with the cross-correlation time-of-flight technique. The angular distribution of CO2 appearing in four peaks in the range 170-400 K shows a maximum in common at the bulk surface normal. It is broader than that perpendicular to the terrace. The translational temperature of CO2 in each peak is much higher than the surface temperature and is maximized at the bulk surface normal. The translational temperature indicates less dependence on the desorption angle than that perpendicular to the terrace. The anisotropy in both angular and velocity distributions is related to the symmetry of reaction sites.