Irradiation of NH3CH4 mixtures as a model of photochemical processes in the Jovian planets and Titan

Photolysis of NH₃ in the presence of CH₄ with a 185-nm light source results in the generation of hot hydrogen atoms that abstract hydrogen from the CH₄ to produce CH₃·. Subsequent reactions of CH₃· and NH₂· give hydrocarbons, CH₃NH₂, and HCN. The extent of reaction of CH₄ was measured by the ratio of the moles of CH₄ reacted per mole of NH₃ decomposed ($\text{Δ}\text{CH}{}_4\text{Δ}\text{NH}{}_3$). This ratio increases with diminishing NH₃ pressure at constant CH₄ pressure but it remains constant if $\text{CH}{}_4\text{NH}{}_3\text{?3}$. The $\text{Δ}\text{CH}{}_4\text{Δ}\text{NH}{}_3$ ratio is independent of temperature in the range 156–298° K, suggesting that hot hydrogen atoms were responsible for the reaction of CH₄. This postulate was confirmed by the observation that this reaction was quenched when H₂ or SF₆ was added to the reaction mixture.