Effects of stimulated emission on radiative transfer with partial redistribution

Abstract

The non-LTE line transfer with stimulated emission is studied. Stimulated emission is important for red transitions in hot stars and infrared transitions in cool stars. The deviation of the absorption and emission profiles from each other is investigated for a two-level atomic model with the line scattering described by the angle-averaged redistribution functions. The partial redistribution formalism has been used while solving the radiative transfer equation. The correct expression for the source function derived by Baschek et al. (1981) has been employed to obtain the emission profile and the radiation field. The redistributiuon function R III gives the emission profile same as that of the absorption profile in the core, and also in the wings, but with a small enhancement at the intermediate frequency points (whether stimulated emission is present or not). The emergent emission profile is different from the absorption profile by several factors in the wings for R II. When stimulated emission is present, it is found that the ratio of the emission profile to the absorption profile and also the intensity in the wings of the spectral lines to be reduced for R II.