Elastic electron scattering by excited hydrogen atoms in a laser field - art. no. 043401

We consider electron scattering by hydrogen atoms in a linearly polarized l aser field. The electrons may have sufficiently high energy in order that t he scattering process can be treated in the first-order Born approximation. The scattered electrons, embedded in the laser field. are described by Gor don-Volkov waves. We assume that during the scattering, the hydrogen atoms are in an excited state (in particular, in the 2s, 2p, or 3s state) and tha t for moderate laser field intensities. it is sufficient to describe the in teraction of the target atoms with the radiation field by first-order time- dependent perturbation theory. We discuss the angular dependence of the non linear differential scattering cross sections for low values N of emitted o r absorbed laser photons, inspecting the contributions of the various elect ronic and atomic terms of the matrix elements. Detailed numerical results a re presented for one-photon absorption at low-field intensities. We also co mpare our results with those obtained from the assumption of a static atomi c polarizability. describing the laser dressing of the excited atomic state s.