Ionization Dynamics and Exchange Effects in Pure Three-Body Coulomb Scattering

Abstract

The measurement of two electrons in coincidence following ionization by electron impact has been performed in a variety of collision geometries [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]. The different cases yield information on different dynamical aspects of the ionization process. Theoretically, upon analysis of ionization mechanisms certain patterns are deduced for the distributions of the vector momenta of reaction fragments. The major obstacle in a theoretical description of such scattering reactions is the inherent non-separability of many-body Coulomb interacting systems. Thus, these systems have to be represented by approximate Hamiltonians and different approximations may well lead to different interpretations of the scattering dynamics. Here we investigate pure three-body Coulombic systems above the complete break-up threshold. A cluster model is adopted in which the three-body system is approximated by three, spatially decoupled, two-body (Kepler) subsystems. This results in the well known 3C-approximation [13, 14]. Coupling between these, in the configuration space, non-interacting two-body (Rutherford) scattering systems can be introduced via position-dependent Sommerfeld parameters [15]. Analyses of the results yielded by these techniques show that dominant structures in the (theoretical) spectra of the outgoing particles can be assigned to the following underlying mechanisms: Single and double-binary collisions Coulomb density-of-state factors interplay between collisional ionization mechanisms and exchange effects Wannier ionization mode Quantum interference between contributing scattering amplitudes and three-body effects.