Irradiation of NH 3CH 4 mixtures as a model of photochemical processes in the Jovian planets and Titan

Abstract

Photolysis of NH 3 in the presence of CH 4 with a 185-nm light source results in the generation of hot hydrogen atoms that abstract hydrogen from the CH 4 to produce CH 3·. Subsequent reactions of CH 3· and NH 2· give hydrocarbons, CH 3NH 2, and HCN. The extent of reaction of CH 4 was measured by the ratio of the moles of CH 4 reacted per mole of NH 3 decomposed ( Δ CH 4 Δ NH 3 ). This ratio increases with diminishing NH 3 pressure at constant CH 4 pressure but it remains constant if CH 4 NH 3 ⪰3 . The Δ CH 4 Δ NH 3 ratio is independent of temperature in the range 156–298° K, suggesting that hot hydrogen atoms were responsible for the reaction of CH 4. This postulate was confirmed by the observation that this reaction was quenched when H 2 or SF 6 was added to the reaction mixture.