Influence of nitrogen on the oxygen dissociation in a DC discharge

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.

Removal of Model Proteins Using Beams of Argon Ions, Oxygen Atoms and Molecules: Mimicking the Action of Low‐Pressure Ar/O2 ICP Discharges

“…The microwave power is held at 40 W and an oxygen flow of 5 sccm is used in this study. Moreover, in order to increase the O atom flux reaching treated samples, an admixture of 0.2 sccm nitrogen is used, which drastically enhances the dissociation degree of oxygen due to a decrease in a wall diffusion loss of O atoms 22, 23. Moreover, it has to be noted that S‐bend shape of the connecting tube avoids direct line‐of‐sight from the microwave plasma to the sample eliminating the exposure of the sample to possible UV and VUV radiation, which is connected with production of excited NO molecules and which can contribute to the proteins removal.…”

Self-Consistent Modeling of Volume and Surface Processes in Air Plasma

“…Using Eqs. (10)(11)(12)(13)(14)(15)(16)(17) and (19)(20)(21)(22), Eqs. (32)(33)(34)(35) can be rewritten in the form…”

“…The interpretation of the Ref. [8][9][10][11][12] experiments requires the development of a kinetic theory for surface processes taking into account different kinds of atoms and surface diffusion of physisorbed atoms. Moreover, because of experimental evidence for the dependence of the probabilities°M on the relative concentrations of different kinds of gas-phase atoms, the development of a self-consistentmodel for gas-phase and surface kinetic processes in low-pressure nonequilibrium plasma becomes important and necessary.…”

Role of admixtures on dissociation of molecular gases

“…Many authors [1,2,3,4,5] demonstrated that even a small admixture can dramatically change the dissociation of the gas. This phenomenon is generally supposed to be caused by one or more of the following effects: change of reduced electric field E/N in the discharge, various homogeneous reactions or by decrease of the wall recombination coefficient due to heterogeneous reactions.…”