Kinetics of the Reactions of F(2P) and Cl(2P) with HNO3

Article abstract of DOI:10.1021/j100319a028

The kinetics of the reactions of HNO3 with fluorine (k₁) and chlorine (k₂) atoms have been studied by using a time-resolved long-path laser absorption technique to monitor the appearence of product NO3 radicals following 351-nm pulsed laser photolysis of X2/HNO3/He mixtures (X = F, Cl).Absolute rate coefficients for the F(²P) + HNO3 reaction have been determined over the temperature range 260-373 K.Between 260 and 320 K, the data are adequately represented by the Arrhenius expression k₁(T) = (6.0 +/- 2.6)*10^-12 exp<(400 +/- 120)/T> cm³ molecule^-1 s^-1.Bet ween 335 and 373 K, the rate coefficient is found to be (2.0 +/- 0.3)*10^-11 cm³ molecule^-1 s^-1 independent of temperature.The observed temperature dependence suggests that reaction proceeds via competing direct abstraction and complex pathways.No NO3 production was observed in the experiments with X = Cl, thus establishing that k₂(298 K) < 2*10^-16 cm³ molecule^-1 s^-1.The Cl(²P) + HNO3 reaction was also investigated by using a pulsed laser photolysis-resonance fluorescence technique to monitor the decay of Cl(²P).Upper limit values for k₂ obtained from these experiments, in units of 10^-16 cm³ molecule^-1 s^-1, are 13 at 298 K and 10 at 400 K.