This paper discusses the connection between the atomic-momentum distribution due to photon recoil and photon statistics. A new formulation is presented based on a Fourier transform with respect to momentum. The asymptotic approximation that is equivalent to a Fokker-Planck treatment is found. Resonance fluorescence is treated in detail. The anomalous diffusion contribution recently found by Ashkin, Gordon, and Cook is separated, and its physical significance is discussed. In particular, it is pointed out that it signifies the coherence between successive photon recoil events. It follows that to obtain the correct diffusion expression one must perform the adiabatic elimination of internal atomic degrees of freedom in the frame moving with the atom, including the deflection caused by light-pressure force. Connections to earlier work are discussed.

• Received 20 December 1982

DOI:https://doi.org/10.1103/PhysRevA.27.2513