Adsorption and Decomposition of Ammonia on a Polycrystalline Tungsten Filament

Adsorption and decomposition of ammonia on a polycrystalline tungsten filament with and without preadsorbed nitrogen doses were studied by flash‐filament desorption spectroscopy. The hydrogen‐desorption spectrum resulting from ammonia decomposition was qualitatively similar to that which would have resulted from a comparable amount of hydrogen dosed onto a clean surface, desorption occurring over much the same temperature range but with a somewhat different spectrum shape. Hydrogen desorption was substantially complete by 900°K under all circumstances. With increasing nitrogen predose, the amount of ammonia taken up in a fixed dosing condition decreased, while total nitrogen left on the surface following the dose increased. Partial decomposition occurred during ammonia adsorption at 300°K resulting in desorption of approximately 1.5 atoms of hydrogen per ammonia molecule absorbed. Prolonged dosage of ammonia on clean tungsten at 300°K left 0.65NH1.5 units on the surface per surface tungsten atom. When tot...

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