Temperature Dependent Rate Coefficient for the Reaction O(3P) + NO2 → NO + O2

The rate coefficient ( k 1 ) for the reaction O( 3 P) + NO 2 → O 2 + NO was measured under pseudo-first-order conditions in O( 3 P) atom concentration over the temperature range 220−412 K. Measurements were made using pulsed laser photolysis of NO 2 to produce oxygen atoms and time-resolved vacuum UV resonance fluorescence detection of O atoms. The NO 2 concentration was measured using three techniques: flow rate, UV absorption, and chemical titration (NO + O 3 → NO 2 + O 2 ). The NO 2 UV absorption cross section at 413.4 nm was determined as a function of temperature using the chemical titration and flow methods. Including the low-temperature data of Harder et al. 1, the temperature-dependent NO 2 cross section is given by σ 413.4 ( T ) = (9.49 − 0.00549 T ) × 10 -19 cm 2 molecule -1 . The measured rate coefficients for reaction 1 can be expressed as k 1 ( T ) = (5.26 ± 0.60) × 10 -12 exp[(209 ± 35)/ T ] cm 3 molecule -1 s -1, where the quoted uncertainties are 2σ and include estimated systematic errors. This result is compared with previously reported measurements of k 1 .