STUDY OF THE KINETICS OF THE REACTIONS OF NO3 WITH HO2 AND OH

The Absolute rate constants for the gas-phase reactions of NO3 with HO2 and OH have been determined using the discharge flow laser magnetic resonance method (DF-LMR). Since OH was found to be produced in the reaction of HO2 with NO3, C2F3Cl Was used to scavenge it. The overall rate constant, k1, for the reaction, HO2 + NO3 --> products, was measured to be k1 = (3.0 +/- 0.7) X 10(-12) cm3 molecule-1 s-1 at (297 +/- 2) K and P = (1.4 - 1.9) torr. This result is in reasonable agreement with the previous studies. Direct detection of HO2 and OH radicals and the use of three sources of NO3 enabled us to confirm the existence of the channel producing OH: HO2 + NO3 --> OH + NO2 + O2 (1a); the other possible channel is HO2 + NO3 --> HNO3 + O2 (lb). From our measurements and the computer simulations, the branching ratio, k1a/(k1a + k1b), was estimated to be (1.0(-0.3)+0.0). The rate coefficient for the reaction of OH with NO3 was determined to be (2.1 +/- 1.0) X 10(-11) cm3 molecule-1 s-1.