Decomposition of Ammonia Photosensitized by Mercury 6(3P1) Atoms

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Abstract
An investigation has been made of the mercury—6(3P1)—photosensitized decomposition of ammonia at room temperature, under both flow and static conditions. Nitrogen and hydrogen were produced in the static experiments; hydrazine was an additional product in the flow experiments. The quantum yield of ammonia decomposition in the flow experiments did not depend on the flow rate but increased in an exponential manner, as the reaction pressure was decreased, from a value of 0.09 at 650 mm toward unity at very low pressures. The quantum yield in the static experiments at high ammonia pressures and at a low extent of reaction was about the same as in the flow experiments at comparable pressures. The static quantum yield decreased when the extent of reaction was increased, when the ammonia pressure was decreased, or when hydrogen was added to the reaction. The percentage of the decomposed ammonia which was recovered as hydrazine increased from zero at low flow rates to 95 percent at high flow rates. At a fixed flow rate, the hydrazine‐to‐nitrogen ratio increased, as the ammonia pressure was increased, from zero to a maximum value which was pressure independent at higher pressures. The hydrazine‐to‐nitrogen ratio increased as the incident intensity of 2537 A radiation was decreased. When ethylene was added to the flow experiments the hydrazine‐to‐nitrogen ratio was markedly increased. However, when platinum wire was introduced into the irradiated zone, the reaction was found to be unchanged. A mechanism is suggested which appears to give the best representation of the results.

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