Inelastic electron-atom collisions in a bichromatic laser field

Inelastic electron-hydrogen atom collisions with the excitation of the 2s and 2p states in the presence of a bichromatic laser field are considered. Resonant and exchange effects are neglected and the problem is treated within the first Born approximation. The interaction of the scattered electron with the laser field is taken into account exactly, while the interaction of the laser field with the hydrogen atom is treated by first-order time-dependent perturbation theory. The contribution of the target intermediate states to the scattering amplitude is taken into account using the Sturmian representation of the Coulomb Green's function. The differential cross sections for the inelastic collision processes are analysed as a function of the relative phase between the two laser field components and it is shown that the influence of the variation of the relative phase is more pronounced than for the elastic scattering analysed earlier (1997 J. Phys. B: Ar. Mol. Opt. Phys. 30 1061). Furthermore, these effects appear at lower laser field intensities and can also be important for larger scattering angles. The symmetry properties of the differential cross section (DCS) as a function of the relative phase are also analysed and the minima of the DCS as a function of the scattering angle are explained by destructive interferences between the undressed part of the scattering amplitude and that part which corresponds to the dressing of the excited state.