Ionization suppression of excited atomic states beyond the stabilization regime

Abstract

A two-dimensional model atom is employed to study the ionization behaviour of initially excited atomic states in intense high frequency laser pulses beyond the dipole approximation. An additional regime of ionization suppression is found at laser intensities where the stabilization effect is expected to break down. The appearance of this effect is due to a strong coupling of the initial wavefunction to the ground state of the cycle-averaged space-translated ionic potential, followed by a subsequent population transfer to the ground state during the laser pulse turn-off. Non-dipole effects are found to increase the overall ionization probabilities, but not to suppress or alter this effect substantially.