Radiative collisions of atoms involving excitation transfer under conditions of small resonance defects

The effective section for transfer of excitation from atom to atom in an external electromagnetic field involving the absorption or emission of a photon is calculated for small resonance defects. The radiative collision line shape is found in the strong and weak field approximations. It is shown that allowance for the angular dependence of the dipole-dipole interaction operator of the atoms appreciably affects the line shape near the resonance