Circular dichroism in differential and integrated cross sections of free-free transitions in high-energy electron-atom scattering

In this paper high-energy electron scattering by hydrogen atoms in the presence of a laser field of moderate power and higher frequencies will be considered. For a superposition of a linearly and a circularly polarized laser beam we shall show that circular dichroism in the angular distribution can be predicted for the nonlinear two-photon transitions, if the dressing of the atomic target by the laser field is treated in second order of perturbation theory in which the coupling between the atomic bound and continuum states plays an essential role. Of special interest is that for particular configurations circular dichroism can be encountered not only in the differential but also in the integrated cross sections. To the best of our knowledge this is the first example of this kind and therefore this effect should become more easily accessible to observation.