Influence of collisional broadening on resonance photoplasma parameters in a sodium-argon mixture

Abstract

A study of photoplasma parameters in a Na–Ar mixture was carried out in a wide range of Ar pressures, considering the Voigt profile of the D1 and D2 resonance lines of Na in the Biberman-Holstein approximation. The effect of collisional broadening on the full width at half maximum (FWHM) of these lines is analyzed in detail, using the constants of the resonance (Na–Na collision) and van der Waals (Na–Ar collision) line shape broadening. 2D simulations of the main parameters (density of resonance (3p) levels of Na; electron density and temperature; photo-EMF) of the resonance photoplasma in a two-chamber cell at the Na pressure 0.02 Torr and Ar pressure 0.1 − 100 Torr have been carried out. It has been established that the difference between these parameters and previously obtained data for the case of the Doppler contour of the resonant line for the exact geometry of the gas cell and gas pressures is significant. Numerically, it reaches one-two orders of magnitude for the electron density and two times for the electron temperature. Also, a noticeable difference in the electron flux spatial picture in the cell for these two cases has been found. Therefore, it is shown that it is necessary to consider the collisional broadening of the resonance line of Na to determine plasma parameters even for relatively small pressures of Na and Ar. The developed approach and obtained data open up an opportunity to make a quantitative design of a photoelectric converter in a mixture of Na–Ar.