1 Isotope Effect in Boudouard Disproportionation Reaction in Optically Pumped CO1

Isotope composition of CO2 produced in CO-Ar mixtures optically pumped by a CO laser in a flow reactor has been analyzed by Fourier transform infrared (FTIR) absorption spectroscopy. Carbon monoxide reactant is a specially prepared, higher-than-natural abundance mixture of 13CO and 12CO isotopomers. Carbon monoxide in the reactor is vibrationally excited by resonance absorption of the pump laser radiation and is vibration-vibration (V-V) pumped up to high vibrational levels. 12CO vibrational level populations and temperature in the V-V pumped region are measured by FTIR emission spectroscopy in a wide range of CO mole fractions in the CO-Ar mixture. In agreement with the anharmonic V-V pumping theory, results of previous optical pumping experiments demonstrate that at these conditions V-V exchange between 12CO and 13CO molecules results in preferential excitation of high vibrational levels of the heavy isotopomer, due to their closer energy spacing. In the present work, 13CO vibrational level populations are calculated using a master equation kinetic model, which predicts the 13CO/12CO relative population ratio on vibrational levels v>20 of approximately a factor of 2. Highly vibrationally excited CO molecules chemically react by Boudouard disproprotionation reaction to form CO2, which at these conditions is expected to be enriched in 13C isotope. Chemical reaction product