Asymmetry, angular and polarization effects in relativistic free-free transitions in a powerful laser field

We reconsider the scattering of electrons by a potential in a strong electr omagnetic plane wave. Since, to a first order of approximation spin effects can be neglected, we describe the scattered electron by a laser-dressed Kl ein-Gordon particle. It is shown that the differential cross sections of in duced and inverse bremsstrahlung are asymmetric with respect to the directi on of propagation of the radiation field. This asymmetry has its origin in the laser-induced drift motion of the electrons. We also find broad dark an gular windows, i.e., scattering angles for which the nonlinear cross sectio ns are marginal. Moreover we demonstrate that at nearly relativistic scatte ring conditions characteristic angular and polarization effects can be enco untered for specific scattering configurations which will not show up in th e non-relativistic case where the radiation field is treated in the dipole approximation. Finally it is shown that even for laser field intensities at which nonrelativistic calculations should apply one can observe discrepanc ies between relativistic and nonrelativistic results.