Resonant scattering of monochromatic light in gases

The frequency dependence of the differential cross section characterizing the resonant scattering of photons by the atoms of a dilute gas has been investigated. It is supposed that the scatterers are sufficiently dispersed so that interference between different scatterers may be neglected. Elastic collisions between the scatterers and the atoms of a buffer gas are treated in the impact approximation. A Maxwell-Boltzmann distribution of velocities is assumed. Analytic expressions for the cross section are obtained in the limits natural width collision width Doppler width, Doppler width natural width collision width, and collision width natural width Doppler width. The significance of these results is discussed.