The resonant scattering of monochromatic light in gases is analyzed. Explicit expressions for the differential cross section are obtained in the limits (Doppler width) ≫ (natural width) ≫ (collision width) and (collision width) ≫ (natural width) ≫ (Doppler width). In the former limit, the frequency distribution of scattered light is narrowed in the forward and backward directions, and has the full absorption width for right-angle scattering. In the collision-dominated limit, the cross section separates into a coherent and a fluorescent component. The motion of the atoms broadens the $\delta$ function distribution characterizing coherent scattering from a stationary target. The interference between light scattered by different atoms is assessed.

• Received 21 August 1968

DOI:https://doi.org/10.1103/PhysRev.178.93