Abstract
The decoupling of electronic orbital angular momentum from the molecular axis in atom-atom collisions is described as a case of rotational coupling between molecular states of different symmetry. For a system A(1S)+B(1P) with not too large an impact parameter, the corresponding semiclassical equations are solved. Explicit predictions are made about the polarisation of the 1P wavefunction from a typical inelastic collision process, that is a process which proceeds through a single molecular state, Sigma or Pi , at small internuclear distance.