1. For linear polarization, this corresponds to the atomic unit of intensity, 3.51 106 W / cm2.
2. For an overview of intense-field laser-atom interactions, and in particular ionization, see: (a) the volume Atoms in Intense Laser Fields, Ed. M. Gavrila (Academic Press, 1992), and the review articles:
3. Atoms in Ultra-intense Laser Fields, by K. Burnett, V.C. Reed, and P.L. Knight, J.Phys. B 26, 561 (1993)
4. Ionization Dynamics in Strong Laser Fields, by L.F. DiMauro and P. Agostini, Adv.At.Mol. Opt.Phys. 35, 79 (1995).
5. Other types of stabilization have been considered in the literature, e.g see the discussion by H.G. Muller in Superintense Laser-Atom Physics IV, Eds. H.G. Muller and M. Fedorov (Kluwer Acad.Publ., 1996), p.1. We shall limit ourselves here to ultra-strong field stabilization. No reference will be made to the classical form of stabilization.