Abstract
The possibility of a complete determination of the scattering amplitudes for a D state produced by a collisionally induced coherent S to D excitation is investigated. A polarisation analysis of the subsequent D to P dipole transition by the photon-particle coincidence method is not sufficient to completely determine the excitation amplitudes for the D state. Additional information can be obtained from collision experiments performed in the presence of symmetry-breaking electromagnetic fields. In the case of Li(3d2D), the combined action of an external magnetic field and the spin-orbit coupling has been utilised. The results of the first coincident level crossing experiment is reported, allowing an unambiguous determination of the excitation amplitudes for the Li(3d2D) state produced in Li-He collisions.