Comparison of spectral line profiles in the models of hard and soft collisions
The qualitative and quantitative effects on the line profile of hard and soft velocity-changing collisions with scattering of absorbing molecules at large and small angles, respectively, are considered. It is shown that in the diffusion model of the profile, known as the model of "soft" collisions, scattering at large angles makes a significant contribution comparable to that in the model of hard collisions. The difference between these traditional models lies only in the mathematical forms of the representation of the collision integral, integral and differential, and the following analytical expressions for the profiles. Simple approximate formulas for the profile were derived and tested, which simultaneously took into account hard and soft collisions.