Collisional-radiative coefficients from a three-level atomic model in nonequilibrium argon plasmas

Abstract

A three-level atomic model is used for determining the steady-state collisional-radiative coefficients in nonequilibrium partially ionized argon plasmas. Rate equations for populations of the atomic levels are coupled to an electron Boltzmann equation that includes inelastic processes. The solution of these coupled equations yields an analytical form for the non-Maxwellian electron distribution function. The reabsorption of radiation in the plasma is included through the use of Holstein radiation escape factors [Phys. Rev. 83, 1159 (1951)]. The cross sections in this model are included in the form of simple analytical expressions obtained from a numerical fitting of available experimental data. The results and limitations of the approach are discussed in a broad range of plasma conditions (electron temperature below 25 000 °K and atomic density of 1014–1018 cm−3).