Showing papers by "James B. Burkholder published in 2004"

Reaction of OH with HO2NO2 (Peroxynitric Acid): Rate Coefficients between 218 and 335 K and Product Yields at 298 K

Abstract: Rate coefficients (k 3 (T)) for the reaction of OH with HO 2 NO 2 (peroxynitric acid, PNA) in the gas phase were measured in the temperature range of 218-335 K by producing OH via pulsed laser photolysis and detecting it via laser-induced fluorescence. The PNA concentration was measured in situ by UV and IR absorption. The H 2 O 2 , HNO 3 , and NO 2 impurities present in the PNA sample were quantified by mass spectrometry and/or UV/IR absorption. The measured value of k 3 (298 K) is (3.4 ′ 1.0) x 10 - 1 2 cm 3 molecule - 1 s - 1 . The temperature dependence of k 3 is best described by the relation k 3 (T) = (8.8 ′ 2.6) × 10 - 1 9 T 2 exp[(1130 ′ 20)/T] cm 3 molecule - 1 s - 1 . The quoted errors for k 3 are at the 2σ level and include estimated systematic errors, which contribute the most to this uncertainty. The measured values of k 3 (T) were independent of pressure between 10 and 100 Torr of helium. The branching ratios of the reaction OH + HO 2 NO 2 → products, for the production of HO 2 and HNO 3 and of NO 3 and H 2 O 2 , respectively, were determined to be <10% and <5%, respectively, at 298 K. Thus, it was deduced that the main pathway for reaction 3 produces H 2 O, O 2 , and NO 2 at 298 K. Our measurements reduce the uncertainties but do not significantly alter the currently calculated impacts of HO 2 NO 2 in the upper troposphere and lower stratosphere. In the course of this study, the rate coefficient for the reaction of OH with H 2 O 2 was measured to be k 4 (T) = (2.9 ′ 1.8) × 10 - 1 2 exp[-(110 ′ 150)/T] cm 3 molecule - 1 s - 1 in the temperature range of 273-356 K.