M-changing collisions in atom-linear molecule collisions

Reports classical trajectory calculations showing that within the sudden approximation, for a wide range of energies and potentials typical of atom or ion-linear molecule interactions, there exists, for each scattering angle, a symmetry axis to which the angular momentum transfer is approximately perpendicular. The author finds that the direction of this axis is well approximated by the bisector of the initial and final directions of the projectile, scattered by the isotropic potential component. The existence of this symmetry axis is a consequence of the short-range forces characterising these collisions and is shown to be less pronounced as the range of the force increases. When near orbiting collisions occur then this symmetry breaks down.