Optical refractivity in Ar-CO2, plasmas at λ=632.8 nm

The refractive index of a high-temperature gas is influenced simultaneously by composition and therefore by temperature. Gas composition data are needed to evaluate the gas temperature. This paper deals with the calculation of equilibrium composition by Gibbs free energy minimization method in Ar-CO2 mixtures at atmospheric pressure in the temperature range between 300 and 4000 K. Next, Ar-CO2 refractivities are computed versus plasma temperature using the relationship between refractivity and temperature obtained by using a state equation and the Gladstone-Dale relation. Finally, a fitting formula for the refractivity as a function of temperature is obtained for each mixture Ar-CO 2.