Reactions of Nitrogen Atoms. I. Oxygen and Oxides of Nitrogen

Several reactions of nitrogen atoms have been investigated in a low‐pressure flow system, using the principle of a ``stirred reactor'' and a mass spectrometer for the determination of steady‐state concentrations. The elementary processes which have been definitely demonstrated to occur and their rate constants are as follows: $$\begin{array}{ccc}\mathrm{N}+\mathrm{NO}={\mathrm{N}}_2+\mathrm{O}& k_1{\text{≥4×10}}^{11}\hspace{0.17em}{\mathrm{cc\; mole}}^{\text{−1}}{\sec }^{\text{−1}}& \text{(1)}\\ \mathrm{N}={\mathrm{O}}_2=\mathrm{NO}+\mathrm{O}& k_8{\text{=2×10}}^{12}\times \exp \text{(−6200/RT)\hspace{0.17em}}{\mathrm{cc\; mole}}^{\text{−1}}{\sec }^{\text{−1}}& \text{(8)}\\ \mathrm{N}+{\mathrm{NO}}_2={\mathrm{N}}_2\mathrm{O}+\mathrm{O}& {10}^{\text{−2}}{k}_1{\mathrm{<k}}_9{\text{<10k}}_1& \text{(10)}\\ \mathrm{O}+\mathrm{NO}={\mathrm{NO}}_2& k_3{\text{≥10}}^{13}\hspace{0.17em}{\mathrm{cc\; mole}}^{\text{−1}}{\sec }^{\text{−1}}& \text{(3)}\\ \mathrm{O}+{\mathrm{NO}}_2={\mathrm{O}}_2+\mathrm{NO}& k_6{\text{≥10}}^{12}\hspace{0.17em}{\mathrm{cc\; mole}}^{\text{−1}}{\sec }^{\text{−1}}.& \text{(6)}\end{array}$$ Unless indicated, the rate constants are at room temperature. The rate constant of nitrogen atom reaction with nitrous oxide is less than 10⁸ cc mole^—1 sec^—1 at 280°; that of oxygen atoms is less than 2×10⁸ at room temperature, neither having been observed to occur. Nitrogen atoms probably react with nitrogen dioxide also by a different mechanism than (10), yielding 2NO and/or N₂+O₂, at a rate which is competitive with (10). Nitrous oxide is probably formed also by another mechanism, which does not involve nitrogen atoms and may well be the reaction of vibrationally excited nitric oxide with nitrogen dioxide. The accommodation coefficient of glass walls, treated with phosphoric acid, for the recombination of oxygen atoms, has been determined as 10^—4 in one reactor and is larger than this in another.