Dynamics of highly charged ions in ultraintense laser fields

Abstract

The dynamics of highly charged ions in a strong laser field are investigated by solving the two-dimensional time-dependent Dirac equation. Relativistic effects are discussed for the hydrogen-like ions with nuclear charges of Z=4, 24 and 79 by considering the changes in the electron trajectory and coherent emission spectrum with changes in the frequency and intensity of the laser field. With increasing Z, the relative field strength between the ionic core and laser fields changes and this results in different characteristics of the dynamical electronic trajectory as well as the corresponding emission spectrum. For an infrared laser field of strength E=8.0 au, the tunneling ionization can hardly be seen for the hydrogen-like ions of Z=24 and only the resonant multiphoton emission spectra below the ionization threshold are predicted. The above threshold harmonics need more intense laser fields or a higher photon energy.