In this paper we present the expressions that have been derived using the Lorentz–Lorenz formula of the dispersion theory and which enable one to calculate the real and imaginary parts of the dielectric constant and refractive index of an arbitrary gaseous mixture. The calculations use experimental data on the absorption spectra of the mixture. These values may be calculated as functions of the incident radiation frequency, including spectral regions involving the absorption lines and bands.
We have shown in our study that the absorption line contour that follows from the dispersion theory does not coincide with the Lorentz contour. We propose that the line contour considered in this paper be called as the Lorentz–Lorenz contour to distinguish it from the Lorentz one.