On parameterization of spectral line profiles including the speed-dependence in the case of gas mixtures

•An algebraic expression for a model line profile was developed.•All main physical factors were taken into account.•The profile's parameters were introduced in the case of gas mixtures.•The nonlinear dependencies of the parameters on pressure were analyzed.

The physically grounded parameterization of a line profile including the speed-dependence was performed. It was shown that two actual parameters of the quadratic speed-dependence appear in gas mixtures instead of a single parameter in a pure gas. One of the parameters is associated with hard elastic velocity-changing collisions; the second is connected with the other sorts of collisions. For comparable concentrations of gas species, they may differ by 50% and depend nonlinearly on partial gas pressures. The dimensionless line narrowing parameter also reveals nonlinear pressure-dependence. The computational expressions for the line profile including all main physical mechanisms of its forming in conditions of gas mixtures are derived.