Coupled channels in the distorted-wave representation

The scattering of electrons or positrons to discrete states of an atomic target is represented in momentum space by coupled integral equations. By introducing a local central potential one may set up a distorted-wave representation for the integral equations, which can be solvled to arbitrary numerical accuracy by quadratures. The perturbative solutions of these equations are the commonly-used distorted-wave first and second Born approximations. The fully-coupled on-shell solution is the distorted-wave unitarized Born approximation. These approximations are tested for charged and uncharged targets. The formalism for inclusion of configuration interaction in the target is described, making a complete theory for electron-atom scattering in a truncated channel space, which can be extended by optical potentials to a fully realistic situation. 19 refs., 4 tabs., 2 figs