Chemical reactions with vibrationally excited carbon monoxide show a marked enhancement over thermal reaction rates. These reactions were studied experimentally, in the gas phase, and on selected surfaces. In addition, vibrational energy transfer between CO (carbon monoxide) and N2 (nitrogen) in cryogenic liquids was studied. For these experiments, energy was partitioned into the vibrational modes of the reactant CO, by absorption of the infrared radiation from a carbon monoxide laser. The product, CO2 (carbon dioxide) from reactions of the vibrationally excited CO molecules was measured. Systematic variation of the vibrational mode energy loading was achieved by adding varying amounts of helium, which provides a channel for fast vibrational relaxation of the higher vibrational levels. The specific rate for the gas phase Boudouard disproportionation reaction CO + CO → CO2 + C, was measured for the vibrationally excited CO reactant, at relatively low gas kinetic temperatures. An activation energy near 6.0 eV (140 kcal/mole) was inferred. Quantitative measurements in the gas phase reaction yield a kinetic rate on the order of koverall = 1.0*10-18 [cm3/sec], for an energy loading of the CO vibrational mode of 0.260 eV/molecule, at a translational mode temperature of 1050 K. For these conditions the vibrational states were in a strongly vibration-to-vibration pumped distribution with at least v = 35 being populated. With this same total vibrational mode energy loading, the rate decreases as higher vibrational quantum levels are quenched by the helium addition. These results are used to determine the validity of a rate based on a transition state theory describing the vibrational quantum state dependence of the chemical kinetic reaction rate.
In other phases of this research, qualitative observations of the vibrationally activated chemistry of the CO on surfaces (copper oxide) have shown a production of CO2, at surface temperatures below 200 °C. At these temperatures, thermal equilibrium reactions on the same surface show no CO2 production. Vibrational mode power loading was also created in cryogenic (87K) liquid CO and argon, and vibration-to-vibration pumping of N2 is observed. An infrared fundamental band spectrum from vibrationally excited N2 has been observed for the first time in emission.
|School:||The Ohio State University|
|School Location:||United States -- Ohio|
|Source:||DAI-A 79/09(E), Dissertation Abstracts International|
|Keywords:||Boudouard, Carbon monoxide, Non-equilibrium, Nonequilibrium, Vibrational, Vibrationally activated chemistry|
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