Atom collisions in a strong electromagnetic field

It is shown that the long-range part of interatomic interaction is considerably altered in a strong electromagnetic field. Instead of the van der Waals law the potential asymptote can best be described by a dipole-dipole R-3 law. Impact broadening and the line shift in a strong nonresonant field are calculated. The possibility of bound states of two atoms being formed in a strong light field is discussed