Differential cross sections for inelastic heavy-particle scattering

The general expression for scattering amplitudes in collisions between systems with internal structure is shown to simplify when the contribution of large relative angular momenta is dominant. The 'elastic approximation' leads to still further simplification. The shortcomings of the elastic approximation are more serious for differential than for total cross sections. For two-state systems a generalization of classical scattering theory can be developed which includes inelastic effects in a way that can be visualized without too much difficulty. The theory is applied to Ne+Na( 2 P 1 2/, 2 P 3 2/) collisions and compared with recent experiments. The interpretation of scattering experiments at larger angles, where classical theory may be inappropriate, is briefly discussed.