The influence of small hydrogen admixtures up to 5 % to a low pressure nonuniform microwave discharge in nitrogen

Abstract

We present the results of spectroscopic and 2D modeling study of the influence of hydrogen addition to non-uniform nitrogen plasma of electrode microwave discharge. The axial intensity distributions of the Ha line and N 2 (2+: C3Πu → B 3Πg, 1+: B3Πg → A3Σ+u) and N2+ (1-: B2Σ+u → X2Σ+g) molecular bands are recorded for different incident microwave power input and hydrogen content. The corona model is used to determine electric field strength in nitrogen discharge from the intensity ratio of 2+ and 1- system of nitrogen bands. By means of 2D modeling spatial distributions of nitrogen molecules in C 3Πu state, microwave field strength, electron density, concentrations of N2+, N4+ are determined in nitrogen and in nitrogen-hydrogen mixtures. The concentration of N2H+ ions in nitrogen-hydrogen mixtures is determined also. The general conclusion of 2D modeling is in agreement with experimental results and shows that the influence of hydrogen addition to discharge is related to the fast conversion reactions of nitrogen ions (N2+, N4+) to N2H+ ion. These ion conversions lead to the change of ion plasma components transport properties, to the modification of microwave field strength in plasma, and consequently, to the alternation of all plasma parameters. © Springer Science+Business Media, LLC 2012.