Interference and correlation in energetic ion-atom collisions: The role of dielectronic processes

Abstract

The influence of electron correlation on interference effects in energetic ion-atom collisions is analyzed. Electron-correlation phenomena are discussed in terms of dielectronic processes which are due to two-electron transitions produced by the electron-electron interaction. The collision systems are treated using the semi-classical approximation up to second order. It is shown that first-order amplitudes are either real or imaginary depending on their symmetries whereas the second-order amplitudes are in general complex. In a multi-electron system, two-step processes produced by the nucleus-electron interaction are shown to proceed via two associated paths canceling important parts of the transition amplitude by interference effects. As an example for the process of single excitation interferences between first- and second-order amplitudes are shown to be influenced by the exchange interaction due to the Pauli principle. Furthermore, double excitation of He and Li is discussed in view of interferences between the nucleus-electron and electron-electron interaction. For Li this interference is expected to be influenced by configuration interaction involved in the states ls2s22S and 1s2p22S.