Vibrational excitation in the CO2 product of the oxidation of CO on platinum: Coverage dependence and implications on reaction dynamics

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Abstract
Vibrational energy distributions in CO2 molecules formed in the catalytic oxidation of CO on platinum have been measured by using a variety of filtering techniques to analyze infrared chemiluminescent emission. For surface temperatures in the range of 650–1100 K the product molecules were vibrationally excited substantially beyond thermal equilibrium with the surface. Emission spectra observed in the 4.3 μm region were significantly red shifted from the fundamental of the asymmetric stretch at 2349 cm−1, indicating that much of the emission originated from higher lying bend–stretch combination states. The vibrational energy of the product, particularly in the asymmetric stretching mode, was sensitive to the coverage of oxygen present on the catalyst surface. These results are consistent with a model in which bending and asymmetric stretching motions contribute strongly to the reaction coordinate for CO oxidation.