Kinetic and mechanistic study of the F atom reaction with nitrous acid

The kinetics and mechanism of the reaction of nitrous acid (HONO) with F atoms have been studied using the mass spectrometric discharge-flow method at 298 K and at a total pressure of 130 Pa of helium. The rate coefficient of the reaction F + HONO --> products (1) was measured under pseudo-first order conditions from the kinetics of HONO decay in excess of F atoms: k(1) = (5.4 +/- 1.1) x 10(-11) cm(3) molecule(-1) s(-1) (quoted uncertainty includes estimated systematic errors). NO2 was detected as a product of reaction (1) and the reaction F + HONO --> HF + NO2 (1 a) was found to be the main (if not unique) channel of reaction (1) under the experimental conditions of the study (k(1a)/k(1) = 1.0 +/- 0.1 (+/-2sigma)). These results indicate that reaction (1) can be a suitable titration reaction for the measurements of the absolute HONO concentrations under laboratory conditions. (C) 2004 Elsevier B.V. All rights reserved.