The Reactive Species in Active Nitrogen

A study has been made of the discrepancy between the N-atom content of active nitrogen as inferred from the maximum HCN production from the reaction of many hydrocarbons, and that indicated by the extent of NO destruction. The HCN production from several hydrocarbons was similar at high reaction temperatures in a spherical reaction vessel, and was independent of reaction temperature in a cylindrical reaction vessel. The ratio (NO destroyed)/(HCN produced) was found to be independent of the mode of excitation òf the molecular nitrogen and of the N-atom concentration, and to be unaffected by the addition, upstream, of N 2 O or CO 2 . Although NH 3 was found to be a minor product of the hydrocarbon reactions, HCN accounted for at least 96% of the N-atom content of the products under conditions where its formation is considered a measure of the N-atom concentration. The NO "titration" value, the maximum extent of HCN production from C 2 H 4 , and the destruction of NH 3 after different times of decay of active nitrogen gave evidence that part of the NO reaction occurred, as does the NH 3 reaction, with excited nitrogen molecules. The long lifetime of the N 2 * species capable of reaction with NO or NH 3 , as calculated from the above data, strongly favors its identification as low vibrational levels of the N 2 (A 3 ∑ u + ) molecule. A consideration of the values for the NO/HCN, NH 3 /HCN, and NH 3 /NO ratios, after different times of decay, for poisoned and unpoisoned systems, suggested that the N 2 * responsible for the NH 3 reaction is formed only during homogeneous recombination of N atoms, while the N 2 * responsible for reaction with NO might be produced by wall recombination as well. Possible reactions of excited molecules present in the active nitrogen – NO system that might lead to decomposition of NO without consumption of N atoms are discussed.