Angular resolved neutral desorption of potassium promoter from surfaces of iron catalysts

摘要: Abstract The angular dependence of neutral potassium emission in the form ground-state atoms as well Rydberg species is studied from a fused iron catalyst. catalyst type used for ammonia synthesis so-called pre-reduced (metallic) condition. distributions observed by surface ionization detection have more peaked shape than cosine distribution expected thermal equilibrium. In case sample industrial process even sharp peak on top found. Using field ionization, i.e. only, rather lobe normal direction A theoretical description cluster formation outside with velocity characteristic equilibrium to interpret results. probably due long-range interaction between formed surface, and clusters are at least partially an excited state. sizes contributing estimated fits experimental main size concluded be quite small, containing just few atoms. There also exist contributions larger around 10–30 gives mainly small clusters, but it does not give Both types number, less 5%, very large 100 according model. data matched single approximately 30 atoms, which indicates that such longer lifetime initial state clusters.