CLASSICAL RESCATTERING EFFECTS IN 2-COLOR ABOVE-THRESHOLD IONIZATION

Rescattering effects in above-threshold ionization such that the electron is driven back to the ionic care by the laser field and rescatters are considered in a completely classical framework, for a laser field consisting of a linearly polarized monochromatic fundamental and its second harmonic, as a function of their relative phase. Several features appear, owing to the two-color field: the energies of the rescattered electrons extend up to 21 U-p, with U-p the ponderomotive potential of the entire held; the angular distributions of the rescattered electrons are no longer symmetric with respect to an interchange of the backward and forward direction and more than one ring or side lobe may appear in either direction; the importance of rescattering can be deduced from the violation of a certain symmetry of the total above-threshold ionization rates fdr fixed energy with respect to the phase between the two fields; the spectra of the rescattered electrons change dramatically when the field intensity is raised from the multiphoton into the tunneling regime.