The asymptotically forbidden transitions Ar(3p⁶¹S₀ ↔ 3p⁵4s³P₂) in the atmosphere of He gas atoms have been taken as a typical example to study the effect of input quantum chemical data variations on radiative characteristics of rare gas quasi-molecules. To this end the spectral profiles and total emission cross sections with and without averaging over Maxwell's distribution have been calculated in a quasi-classical approach for different sets of the input quantum chemical data obtained in semi-empirical and RECP-MRDCI approaches. It has been demonstrated that the effect of the variations of quantum chemical data depends on which radiative characteristic is under consideration and on the region of interatomic distances. Thus, conclusions regarding the quality of the quantum chemical input data, based on comparisons with experimental results or the deduction of potential energy curves and/or radiative widths from experiments or fitting procedures, must be preceded by the study of the interatomic distance regions that are most important for a specific experiment.