Atomic collision theory. Course 3

The scattering of a particle by a central potential is considered first from a purely classical viewpoint, and the concept of the scattering cross section is introduced. It is shown that, for most applications to the study of the interstellar medium, a full quantal treatment of the collision problem is generally necessary and the quantum mechanical analysis of scattering by a central potential is given. Collisions between electrons and hydrogenic ions are considered as an illustration of the application of the quantum mechanical method to problems of scattering by a real potential. Modifications introduced by the finite electron spin and the indistinguishability of the two electrons are briefly discussed. The Kohn variational principle, which enables approximate solutions to the collision problem to be found which are of sufficient accuracy for intended astrophysical applications, is covered. 1 fig, 7 refs