Mass Spectrometric Studies of Atom Reactions. I. Reactions in the Atomic Nitrogen-Ozone System

Abstract

A method has been developed for following the kinetics of fast atomic reactions with a mass spectrometer. The method has been used to determine separately the rate constants for the following reactions which are relevant to an atomic nitrogen‐ozone system. $$\begin{array}{cc}\mathrm{N}+{\mathrm{O}}_3\to \mathrm{NO}+{\mathrm{O}}_2& k_1{\text{=(5.7±1.4)×10}}^{\text{−13}}\hspace{0.17em}{\mathrm{cm}}^3{\mathrm{molec}}^{\text{−1}}{\sec }^{\text{−1}}\\ \mathrm{N}+\mathrm{NO}\to {\mathrm{N}}_2+\mathrm{O}& k_2{\text{=(2.2±0.6)×10}}^{\text{−11}}\hspace{0.17em}{\mathrm{cm}}^3{\mathrm{molec}}^{\text{−1}}{\sec }^{\text{−1}}\\ {\mathrm{O}}_3+\mathrm{NO}\to {\mathrm{NO}}_2+{\mathrm{O}}_2& k_3{\text{=(2.1±0.5)×10}}^{\text{−14}}\hspace{0.17em}{\mathrm{cm}}^3{\mathrm{molec}}^{\text{−1}}{\sec }^{\text{−1}}\\ {\mathrm{O}}_3+\mathrm{O}\text{→2}{\mathrm{O}}_2& k_4{\text{=(2.5±0.5)×10}}^{\text{−14}}\hspace{0.17em}{\mathrm{cm}}^3{\mathrm{molec}}^{\text{−1}}{\sec }^{\text{−1}}\\ \mathrm{O}+{\mathrm{NO}}_2\to {\mathrm{O}}_2+\mathrm{NO}& k_5{\text{=(2.5±0.6)×10}}^{\text{−12}}\hspace{0.17em}{\mathrm{cm}}^3{\mathrm{molec}}^{\text{−1}}{\sec }^{\text{−1}}\end{array}$$ These reactions have been used to interpret the observed changes of concentration with time for reactants and products of the N–O₃ reaction. The concentrations of N₂O and NO₂ in the system were below the detection limits of the mass spectrometer, which is consistent with predictions based on the above rate constants. Evidence was obtained for the production by reaction (2) of vibrationally excited N₂ molecules having energies greater than 23.4 kcal/mole. Such energetic molecules are not present in significant quantities in discharged O₂ or N₂.