Light polarization effects in laser-assisted (e, 2e) collisions in helium

The influence of laser polarization on the triple differential cross sectio n (TDCS) for electron impact ionization of helium is analysed in the asymme tric coplanar geometry. The interaction of the laser field with the inciden t, and scattered electrons is treated non-perturbatively by using Volkov wa ves, while that of the ejected electron moving in the combined field of the residual ion He+ and of the laser is obtained by using the ansatz formulat ed by Joachain et al (1988 Phys. Rev. Lett. 61 165) for the case of atomic hydrogen. The remaining interactions are treated by using first-order pertu rbation theory. Detailed calculations of the scattering amplitudes are perf ormed for a helium target. We discuss the influence of the laser polarizati on on TDCS as a function of the angle of ejection of the slow electron for selected choices of the laser frequency and number of photons exchanged bet ween the external field and the electron-helium system.