Ionization of a hydrogen atom from its ground state by a coherent bichromatic laser field

We study the "coherent phase control" between the three-photon ionization b y a fundamental laser field and the one-photon ionization by its third harm onic for a hydrogen atom in its ground state. The relative phase delta of t he harmonic field with respect to the fundamental laser radiation "modulate s" the interference between the two ionization channels, which is important near the crossing points between the ionization rates of the two individua l processes. Numerical results for the total ionization rate and for the an gular distribution of the photoelectrons as a function of the phase delta a re presented for frequencies located in the vicinity of the atomic resonanc es corresponding to the absorption of two laser photons.