Asymmetries and dark angular windows in relativistic free-free transitions in a powerful laser field

We consider potential scattering of electrons in a powerful laser field. The laser-dressed electron is described by the solution of the Klein-Gordon equation in a powerful plane-wave radiation field. The scattering process is treated in the first Born approximation. It is shown that the differential cross sections of induced and inverse bremsstrahlung are asymmetric with respect to the direction of propagation of the radiation field. This asymmetry has its origin in the laser-induced drift motion of the electrons and should, by present day experimental standards, become an observable effect. Numerical calculations also show the existence of broad dark angular windows, i.e., scattering angles for which the nonlinear cross sections are marginal. The positions of such windows depend on the laser field intensity as well as on the nonlinearity of the laser-induced scattering process.