Strong potential second Born theory for electron loss to the continuum in collision with heavy targets

Abstract

A second-order Born theory is formulated for the description of forward electron emission from a light projectile in energetic collision with a heavy target atom. This theory is termed 'strong potential second Born theory' (SB2) because it accounts for electron propagation in the strong target potential. It is evaluated for the singly inelastic contribution to electron loss, while the first Born approximation is used for the simultaneous projectile-target excitation. From the SB2 theory, the 'impulse approximation' of Hartley and Walters (1987) is derived. By comparison with experimental data for the He++Ar system it is shown that both theories account well for the electron intensity while the asymmetry of the forward peak is only correctly given by SB2. For larger emission angles, consideration of the target potential in the electronic final state is of increasing importance. Then the SB2 becomes inferior to the electron impact approximation.