Perturbation theory for three-particle Coulomb scattering

The Born series and multiple scattering expansion for the off-shell wave functions corresponding to a system of three charged particles are studied. Explicit expressions are derived for the anomalous terms and divergences which occur in these perturbation expansions in the energy-shell limit. A prescription is given for canceling these anomalous terms. The resulting ''renormalized'' perturbation expansions are used to formulate various approximations to the T matrices for excitation and ionization of a neutral fragment by a charged particle. (author)