Dipole force with retarded phase in a standing wave

The radiation force on a two-level atom in a standing wave was calculated, and the general expression of the radiation force without spatial average was given. It was shown that the zero-order force corresponds to the simulated radiation force, while the first-order force to the dipole force, and the higher-order force can be neglected. The magnitude and phase of the dipole force were given, and the dependence of phase on the atom velocity was discussed which affects the dynamics of atoms in a standing wave. The phase dependence on the atom velocity was explained with the photon redistribution model.