Gas-phase Boudouard disproportionation reaction between highly vibrationally excited CO molecules

The gas-phase Boudouard disproportionation reaction between two highly vibrationally excited CO molecules in the ground electronic state has been studied in optically pumped CO. The gas temperature and the CO vibrational level populations in the reaction region, as well as the CO2 concentration in the reaction products have been measured using FTIR emission and absorption spectroscopy. The results demonstrate that CO2 formation in the optically pumped reactor is controlled by the high CO vibrational level populations, rather than by CO partial pressure or by flow temperature. The disproportionation reaction rate constant has been determined from the measured CO2 and CO concentrations using the perfectly stirred reactor (PSR) approximation. The reaction activation energy, 11.6 +/- 0.3 eV (close to the CO dissociation energy of 11.09 eV), was evaluated using the statistical transition state theory, by comparing the dependence of the measured CO2 concentration and of the calculated reaction rate constant on helium partial pressure. The disproportionation reaction rate constant measured at the present conditions is k(f) = (9 +/- 4) x 10(-18) cm(3)/s. The reaction rate constants obtained from the experimental measurements and from the transition state theory are in good agreement. (c) 2006 Elsevier B.V. All rights reserved.