NASA - National Aeronautics and Space Administration

A laser flash photolysis–resonance fluorescence technique has been employed to investigate the kinetics and mechanism of the reaction of electronically excited oxygen atoms, O(1D), with CF2HBr. Absolute rate coefficients (k1 ) for the deactivation of O(1D) by CF2HBr have been measured as a function of temperature over the range 211–425 K. The results are well described by the Arrhenius expression k1 (T) = 1.72 ϫ 10Ϫ10 exp(+72/T) cm3molecule-1s-1; the accuracy of each reported rate coefficient is estimated to be Ϯ15% (2␴). The branching ratio for nonreactive quenching of O(1D) to the ground state, O(3P), is found to be 0.39 Ϯ 0.06 independent of temperature, while the branching ratio for production of hydrogen atoms at 298 K is found to be 0.02+0.01-0.02. The above results are considered in conjunction with other published information to examine reactivity trends in O(1D) + CF2XY reactions (X,Y = H, F, Cl, Br).