The surface recombination of nitrogen atoms on various materials was investigated at atmospheric pressure. The afterglows of pure nitrogen discharge are injected into a surface loss test unit, whose path wall is composed of the materials to be examined. Measurement of the nitrogen atom densities at several points in the flowing afterglows reveals the temporal decay characteristics. The results are compared with two-dimensional numerical simulations to obtain the surface loss probability γ. Among the seven materials we studied (stainless steel, aluminium, titanium, alumina, Pyrex glass, aluminium nitride and boron nitride), stainless steel was found to have the highest γ value: 1.8 × 10−3; the lowest was for boron nitride: 4.8 × 10−5. The dependence of γ on surface roughness and temperature was also examined.

A method has been developed for real-time measurement of nitrogen atom density in atmospheric pressure post-discharge flows. In this method, nitric oxide is supplied to the downstream of a nitrogen discharge as a reactant. Our chemical simulation has revealed that the injected nitric oxide is consumed mainly by reductive reaction with nitrogen atoms or oxidative reaction with oxygen atoms. The number density of atomic nitrogen is determined almost instantaneously through the measurement of nitric oxide and nitrogen dioxide densities with a gas analyser. The experimental verification was carried out with a dielectric barrier discharge unit as a nitrogen atom source, and the results showed good agreement with simulation predictions.

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