Resonant multiphoton ionization of the 1s state of a hydrogen atom in a strong laser field

The process of resonant multiphoton ionization of a hydrogen atom in the gr ound 1s state is studied by direct numerical integration of the nonstationa ry Schrodinger equation for a quantum system in an electromagnetic field. T he dependence of photoionization probability on the radiation intensity is found to be nonmonotonic. It is established that the minima of ionization c orrespond to multiphoton resonances between the ground state and one of the excited (Rydberg) atomic states perturbed by the laser field. it is shown that ionization is suppressed due to rearrangement of Rydberg states in a s trong electromagnetic field and is accompanied by efficient Raman Lambda tr ansitions, which connect a set of closely lying Rydberg states via the cont inuum. (C) 2000 MAIK "Nauka/lnterperiodica".