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

Abstract

Nitrogen oxides, NO and NO{sub 2} (collectively called No{sub x}), play a crucial role in atmospheric ozone chemistry: they lead to photochemical ozone production in the troposphere and catalytic ozone destruction in the stratosphere. The rate coefficient (k{sub 1}) for the reaction O({sup 3}P) + NO{sub 2} {r_arrow} O{sub 2} + NO was measured under pseudo-first-order conditions in O({sup 3}P) atom concentration over the temperature range 220--412 K. Measurements were made using pulsed laser photolysis of NO{sub 2} to produce oxygen atoms and time-resolved vacuum UV resonance fluorescence detection of O atoms. The NO{sub 2} concentration was measured using three techniques: flow rate, UV absorption, and chemical titration (NO + O{sub 3} {r_arrow} NO{sub 2} + O{sub 2}). The NO{sub 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., the temperature-dependent No{sub 2} cross section is given by {sigma}{sub 413.4}(T) = (9.49 {minus} 0.00549 T) {times} 10{sup {minus}19} cm{sup 2} molecule{sup {minus}1}. The measured rate coefficients for reaction 1 can be expressed as k{sub 1}(T) = (5.26 {+-} 0.60) {times} 10{sup {minus}12} exp[(209 {+-} 35)/T] cm{sup 3} molecule{sup {minus}1}more » s{sup {minus}1}, where the quoted uncertainties are 2{sigma} and include estimated systematic errors. This result is compared with previously reported measurements of k{sub 1}.« less