Diode laser absorption study of internal energies of CO2 produced from catalytic CO oxidation

Internal energy distributions for CO2 molecules produced in the catalytic oxidation of CO by O-2 on polycrystalline platinum have been directly measured using a high resolution tunable diode laser (TDL) spectrometer. Absorption spectra have been collected for CO2 produced in a flow cell reactor for a wide range of temperatures and reactant ratios. Vibrational energies for CO2 produced under most reaction conditions are greater than would be expected from complete equilibration with the surface. The asymmetric stretching mode consistently exhibited a higher vibrational Boltzmann ''temperature'' than the bending or symmetric stretching modes. The level of vibrational excitation for all of the vibrational modes was sensitive to oxygen coverage, i.e. as either the O-2:CO reactant ratio or the surface temperature is increased, the vibrational temperature of the product CO2 increases significantly. (C) 1996 American Institute of Physics.