The CF3+NO2 rate constant measured between 1.5 and 110 Torr and between 251 and 295 K by time resolved infrared emission

The rate constant k(1) for reaction of CF3 with NO2 was investigated over t he pressure range 1.5-110 Torr Ar or N-2 and at temperatures between 251 an d 295 K. Time resolved emission from vibrationally excited CF2O and FNO pro ducts was used as a detection method for CF3 removal. The rate constant at room temperature shows no marked variation with pressure, with an average v alue of k(1)=(1.75 +/-0.26)x10(-11) cm(3) molecule(-1) s(-1), where the err ors are 2 sigma, but a small reduction at the lowest pressure indicates the possible contribution from a third body recombination process. We conclude that this process is minor, and if it is treated as a separate reaction ch annel it results in a limiting high pressure branching ratio of 13 +/-7%, w hich drops to half that value at 10 Torr. As the limiting high and low pres sure rate constants are within the 2 sigma error bars of k(1), we recommend the average value as applying over the full pressure range. Combination wi th previous results shows that of the possible bimolecular channels, format ion of CF2O+FNO dominates (ca. 95%). No temperature dependence is seen, wit hin experimental error. Pitfalls in the extraction of rate constants from t he analysis of time resolved product emission are discussed, and a method i s described to assign rate constants unambiguously to reactive formation an d collisional quenching. CF3 radicals were formed from the 248 nm photolysi s of CF3I, and observations of emission from the radical show previously un observed excitation in the asymmetric C-F stretching mode nu (3).