Within the framework of the line wing theory, the line shape parameters related to the intermolecular interaction potential are obtained from a comparison between the calculated and measured absorption coefficients. At the same time, the relations for the characteristics considered as parameters in the line wing theory can be obtained from the general expression for the absorption coefficient in terms of the Moller operators taking into account the line mixing effect. These relations have a simple form in the case of no line mixing and can be easily estimated. Their comparison with the values obtained from approximation of the experimental data on the absorption coefficient, which implicitly include the line mixing, is indicative of its inessential role in the case of the 4.3 mkm CO2 band considered in this paper.