Surface-catalyzed formation of electronically excited nitrogen dioxide and oxygen

Abstract

The surface-catalyzed recombination of NO and O atoms to produce excited NO/sub 2/ molecules has been studied. By using the reaction of N atoms with NO (N + NO ..-->.. N/sub 2/ + O), the O atoms were produced in the absence of molecular oxygen. The resultant orange glow attributed to the electrically excited NO/sub 2/ molecules was observed directly over a nickel metal catalyst in a flow system operated in the 20 mtorr range. Measurements of the attenuation of the intensity as a function of distance from the catalyst yielded an observed effective lifetime of approximately 79 ..mu..s, which is in the range of radiative lifetimes of NO/sub 2/. The Herzberg emission from the O/sub 2/ (A/sup 3/ ..sigma../sub u//sup +/) state was observed as a function of distance from the catalyst surface. With increasing O-atom concentration the observed effective lifetime appears to increase. When the reaction of NO with N atoms was used to produce O atoms at the equivalence point, i.e., with no excess NO and N atoms, no Herzberg emission was observed. 39 references, 7 figures.