Algebraic approximation of the spectral line profile with allowance for hard and soft speed-related collisions

An algebraic approximation has been obtained for a spectral line profile derived with allowance for collisions with scattering both at large and small angles. In the region of practically significant parameters, deviations of the approximate profile from the exact calculation do not exceed a tenth of a percent. It is shown that soft collisions with scattering at classical small angles reduce the effect of the collisional narrowing of lines owing to which the line profile becomes flatter as compared to the profile in the model of hard speedrelated collisions. The relative difference between maximum amplitudes of these profiles can reach 15%, which leads to the necessity to take into account soft collisions together with hard collisions in the quantitative processing of high-resolution spectra under conditions of nonuniform broadening of the lines. © 2015, Pleiades Publishing, Ltd.