Influence of nitrogen on the oxygen dissociation in a DC discharge

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Abstract
The effect of the addition of molecular nitrogen on the oxygen dissociation is investigated in a low pressure gas discharge. The dissociation efficiency is measured as a function of N2 concentration, for a total pressure ranging from 0.4 to 3 Torr in discharge tubes with diameter between 6 and 21 mm. The concentration of O atoms is obtained by the NO+O chemiluminescent reaction. The authors show that for a few percent of nitrogen the oxygen dissociation degree varies by a factor of 1.5-10 depending on the nitrogen concentration, tube diameter and total pressure. The ratio of the dissociation degree for pure oxygen and mixtures of oxygen and nitrogen is calculated, and the authors show that their results imply that, as the tube diameter tends to infinity, the dissociation efficiency tends to one. The authors conclude that the most important reason for the increase in the dissociation of oxygen in the presence of nitrogen is the reduction of wall diffusion losses.