Collisional redistribution of light: A comparative study of the density operator and optical collisional approaches

We present an outline of both the redistribution theory and the optical collision approaches. Starting from the general theory of collisional redistribution we show how it reduces to the weak-field binary-collision limit. The optical collision method is discussed here for the case of a degenerate atom perturbed by e.g. a rare gas. This approach also provides a natural basis for a nonadiabatic theory of collisionally broadened lineshapes. The connection between both approaches is demonstrated by the equivalence of the collision operator of redistribution theory and the scattering matrices for optical collisions. As applications the quasistatic limit of the theory and the depolarization of the fluorescence for the model adiabatic reorientation are discussed.