Continuum distorted-wave method in the two-electron charge exchange theory

Abstract

Introduction. In the case of collisions with multi-charged ions of atoms, more complex than the hydrogen atom, other than single-electron charge exchange and ionization, other processes may occur. These are, first of all, the processes of two-electron capture, capture with simultaneous ionization or ion excitation and others. We shall stop on the problems of the theoretical description of the processes of two-electron capture in the region of intermediate and high collision velocities of ions with atoms. Purpose . Research the interactions of multi-charged ions with atoms in the region of intermediate and high collision velocities using theoretical methods. Methods. To describe the double charge exchange processes in high-energy ion-atom collisions a four-part formalism of continuum distorted-wave method (CDW-method), based on the integral Dodd-Graider's equations, were developed. Results. We obtained a matrix element that describes the two-step (Thomas) mechanism of electron capture through a continuous spectrum from a target atom into bound states relative to the fast -particle. For the reaction amplitude, in the approximation of the mechanism of simultaneous capture of two electrons, a general expression that takes into account Coulomb effects in the initial and final states is found. Conclusion. The application of the general theory is illustrated by the example of a two-electron charge exchange reaction in collisions of helium atoms with -particles. The results of calculations of the cross sections are in good agreement with the experimental and theoretical data. An attractive side of the proposed formalism is the consistent consideration of the asymptotics of wave functions in both channels of the reaction, which takes into account the long-range nature of the Coulomb interactions.