Theory and calculations of selective specular reflection for a multilevel model and a model of a two-component gas

The Schuurmans theory of selective specular reflection is generalized to the case of reflection from a medium composed of multilevel atoms. The reflection spectrum given by this theory is demonstrated. In this theory, which is linear in the field, the reflection linewidth is a nonlinear function of the density of the atoms. The reason is that the Doppler broadening and the collisional broadening make nonadditive contributions to the linewidth. The results of numerical calculations show the limits of applicability of the approximate expressions of the Schuurmans theory for interpreting experiments. The Schuurmans theory is also generalized to the case of selective specular reflection from a two-component medium consisting of working and buffer atoms. The case of an additional narrowing of the reflection line (due to the wings) is discussed.