Speed-dependent spectral line profile including line narrowing and mixing

•An algebraic expression for a model line profile was developed.•All main physical factors were taken into account.•The roles of soft and hard collisions were analyzed.•Some of profile׳s parameters were calculated and declared as fixed.

A line profile model was developed that accounts for all essential underlying physical mechanisms. The model is based on the quantum-mechanical collision integral kernel calculated for intermolecular interaction potentials ∝r−n with n=3…6 where r is the distance between colliding molecules. It was shown that collisions of molecules with scattering on classical small angles flatten the line profile. The relative flattening reaches 10% for n=3 and has a smaller value, ~2%, for n=6 in conditions of inhomogeneous line broadening. An algebraic expression for the line profile was obtained, which allows processing recorded spectra with preliminary estimation and constraint of some of the profile׳s parameters.