Electron capture in collisions between negative and positive ions

Collisions between negative and positive atomic ions are investigated. The ionic wave function is expressed in terms of the Coulomb Green's function. Normalizing this function allows the system of two ions to be described com pletely. The exchange matrix elements turn out to be the sums of products o f the Coulomb wave functions over degenerate states. These sums are express ed in terms of the quadratic form of the wave function for a state with zer o angular quantum numbers, l = m = 0. The nonadiabatic coupling of quasi-cr ossing terms with other terms of the system is analyzed; this effect signif icantly increases the cross section for single-electron capture. (C) 2001 M AIK "Nauka/Interperiodica".