Kinetic studies of the reactions of NO, (1) and of NO₂, (2), with N ⁴S atoms have been made using direct mass spectrometric detection of N atoms in a discharge flow system. The rate constant k₁(cm³ molecule^–1 s^–1) for the rapid reaction (1), N + NO [graphic omitted] N₂+ O (1), has been determined with pseudo first-order kinetic analysis ([NO]₀/[N]₀ 1). The mean value for k₁ was (2.2 ± 0.2)× 10^–11 at 298 K, and between 298 and 670 K, k₁ was given by the expression (8.2 ± 1.4)× 10^–11 exp[–(410 ± 120) K/T].

Similar kinetic studies of the N + NO₂ reaction, using pseudo first-order analysis with very large excesses of NO₂([NO₂]₀/[N]₀ > 80), showed the rate constant for this reaction to be an order of magnitude less than the literature value. However, at lower values of [NO₂]₀/[N]₀, much greater apparent rate constants for the N + NO₂ reaction were obtained, similar to those found previously. These high values are attributed to a rapid catalytic cycle capable of removing both N atoms and NO₂, i.e., N + NO₂ [graphic omitted] N₂O + O (2A), O + NO₂ [graphic omitted] NO + O₂(3), N + NO [graphic omitted] N₂+ O (1). Reactions (1)+(3) have the stoichiometry, N + NO₂→ N₂+ O₂: No evidence was found from N₂O yields in the N + NO₂ reaction for any reactive channel involving N + NO₂ other than reaction (2A). The results give a mean value for k_2A equal to (1.4 ± 0.2)× 10^–12 cm³ molecule^–1 s^–1 at 298 K.