Direct laser ion acceleration and above-threshold ionization at intensities from 1021 W/cm2 to 3 × 1023 W/cm2

Calculations on the dynamics of ions and electrons in near-infrared laser fields at intensities up to 3 × 1023 W/cm2 are presented here. We explore the acceleration of ions in a laser focus by conservation of canonical momentum during ionization events and by the ponderomotive force in the f/1 focal geometry required to reach such intensity. At intensities exceeding 1023 W/cm2, highly charged ions are expelled from the laser focus before they can interact with the laser pulse at peak intensity, decreasing the predicted ionization yields of deeply bound states. We consider the interaction of a tightly focused, f/1 laser pulse with krypton at an intensity of 3 × 1023 W /cm2 and a pulse duration of 140 fs.We find that the ions and electrons are accelerated to energies in excess of 2 MeV/nucleon and 1.4 GeV, respectively. Ponderomotive expulsion of the parent ions decreases the total number of ultrarelativistic above-threshold ionization electrons produced by tunneling ionization from the K-shell states of krypton but does not change their energy spectrum.