The orientational dichroism in (e, 2e) collisions: interplay between geometrical and dynamical effects

The fully differential cross sections for the electron-impact ionization of atomic targets, prepared in a given circular state using laser-pumping, re veal a dependence on the inversion of the helicity of the exciting photon. This 'dichroism' effect was shown to be strongly dependent on the geometric al arrangements of the experiment bath theoretically and experimentally In addition, as shown theoretically in this paper, the dichroism may also vani sh at certain 'non-geometrical' points that can be deduced analytically wit hin the first Born approximation. More elaborate calculations using the dis torted-wave Born approximation confirm this analysis. On the basis of this study, we further suggest a possible explanation for a structure observed r ecently in the state-resolved fully differential cross sections for a sodiu m target.