Suppression of non-sequential multiple ionization at relativistic laser intensities

Abstract

The majority of experiments on atomic ionization dynamics in strong laser fields have been performed at laser intensities below 1016 W/cm2[l]. The strong doubly and multiply charged ion yields measured for atomic systems at intensities below the saturation intensity result from a non-sequential ionization process, which is by orders of magnitude larger than the sequential one [2]. This process is well understood in terms of a rescattering model [3], The model provides an intuitive qualitative picture of the ionization mechanism: In a first step one electron is set free by tunneling ionization, which is quantitatively described by a single active electron tunneling formula [4]. Depending on the phase of the laser field at which the electron is released it gains energy from the field and returns to the core. Upon rescattering further electrons are ionized. Recently, very detailed differential measurements on the momentum distribution of the ions [5] have been explained on the basis of this model [6].