Suppression of ionization and atomic electron localization by short intense laser pulses

Ionization suppression and electron localization have been observed in numerical modeling of two-photon ionization by very intense short-wavelength laser fields. In this paper we present similar results for one-photon ionization. We find that a one-dimensional atom follows one of three distinct routes to ionization depending whether the field is weak, strong, or superstrong. The first route can be described by perturbation theory. The second route is characterized by very rapid depletion of the bound-state population, leading to 100% ionization. The third route features incomplete ionization and electron localization. The behavior of the atom in both strong and superstrong fields is strongly correlated with the deformation of the atomic binding potential associated with the Kramers-Henneberger frame transformation.