Inelastic dipole-dipole scattering in the sudden approximation

The time-dependent sudden approximation is applied to dipole-dipole scattering. It is shown to be reducible to an analytic form of extreme simplicity, allowing rotor-rotor inelastic cross sections to be calculated with minimal effort. The possibility of correcting the method to allow for adiabaticity is explored, and an optimal procedure is given. Comparison with close-coupling calculations for HF-HF is made, and two classes of transition are identified, those of 'resonant' and 'non-resonant' character, respectively. For the latter, the adiabatic correction is successful, while for the former it fails badly. A physical explanation for this failure is offered.