CLASSICAL AND QUANTUM STABILIZATION OF ATOMS IN INTENSE LASER FIELDS

With the help of phase-space pictures we consider the dynamics of a hy drogen atom driven by a high-frequency periodic electromagnetic field. We show that the stabilization phenomenon, widely discussed in the li terature, has quantum and classical appearances, which correspond to d ifferent physical situations. Classical stabilization relies on the dy namics of the electron in the laser-induced effective potential: the e lectron repeatedly crosses the separatrix of the Coulomb potential mov ing along the trajectories of the effective potential. Quantum stabili zation results from the decrease of matrix elements of multiphoton tra nsitions, which implies a decrease of the net cross section of multiph oton photoeffect from the new stationary states of the effective poten tial.