Semiclassical model of the electron-impact ionization of hydrogen in the presence of a strong laser field

Electron-impact ionization of hydrogen in the presence of a strong laser fi eld is studied in the framework of the time-dependent Hartree-Fock theory. The probability distribution of the impact electron is further approximated by a plane circular disk, moving on a classical path along the polarizatio n direction of the laser field. The remaining time-dependent Schrodinger eq uation for the hydrogen atom is solved numerically by finite-difference met hods for different impact parameters, electron energies, and laser intensit ies. The integrated cross section for field-free impact ionization is found to agree remarkably well with previous results in the intermediate and hig h energy range (60-600 eV). Field ionization and collisional ionization can be simultaneously calculated with this model. [S1050-2947(99)03111-X].