Self-absorption quantification in the case of SF6–N2 thermal plasma mixture

Abstract

A simple and accurate method is presented to estimate quantitatively the self-absorption effect for the emission radiations from nitrogen in the case of SF6–N2 plasma mixture. The self-absorption phenomena of optically thick lines are treated parametrically on the basis of escape factor. The resonance escape factors for bound–bound transitions for the lines emitted by atomic nitrogen at 113.5, 119.96, 124.32, 149.26 and 174.53nm are calculated assuming Voigt line shape. The escape factors for free-bound (continuum) radiation which have been the object of fewer investigations are also considered. The escape factors are calculated as a result of the solutions of the equation of radiative transfer which is independent from any special geometry. Assuming a constant plasma size the dependence of escape factors on the temperature, pressure and the nitrogen proportion in SF6 plasma are also taken into account. These calculations may be useful in plasma modeling and diagnostics as well as the application of laser-induced plasma spectroscopy (LIPS) used in the quantitative analysis of elemental compositions.