On one-dimensional velocity approximation for speed-dependent spectral line profiles

An application of one-dimensional velocity approach to calculation of speed-dependent spectral line profiles was considered. It was shown that a mean deviation of the line profile obtained within this approach from the line profile derived with integrating over three projections of an absorbing molecule's velocity does not exceed 1.1% at mass ratios of perturbing and absorbing molecules ≤9. Analytical approximate expressions for speed-dependent line profiles, including spectral line narrowing and mixing, were obtained for one- and three-dimensional velocity approaches.