Velocity Dependence of the Scattering Amplitudes in Resonant Collisions

The forward scattering amplitude for the two-body resonant collision is calculated as a function of the relative velocity. The interaction is assumed to be the long-range dipole–dipole, together with a short-range repulsive core. The quantum as well as semiclassical calculations are performed, and the validity of the existing calculations is discussed. Application of the results to the problem of resonance broadening is considered in detail.