Twofold angular distributions in two-color, two-photon ionization

The ejected electron angular distributions for two-color ionization of hydrogen are studied using a new approach which takes into account the radiative corrections to both the bound and the continuous states. One considers ionization processes in which one high frequency, linearly polarized photon has enough energy to ionize the atom, meanwhile, one extra-photon is exchanged between the atomic system and the low frequency, circularly polarized field. Asymmetric angular distributions are predicted for this case and their origin is discussed. Numerical evaluations, made for the Nd:YAG laser and high frequencies which are near the value of the ionization threshold are presented. (author). 34 refs, 2 figs