Very-high-order harmonic generation from Ar atoms andAr+ions in superintense pulsed laser fields: Anab initioself-interaction-free time-dependent density-functional approach

Abstract

We present an ab initio nonpertubative investigation of the mechanisms responsible for the production of very-high-order harmonic generation (HHG) from Ar atoms and ${\mathrm{Ar}}^{+}$ ions by means of the self-interaction-free time-dependent density-functional theory recently developed. Further, by introducing an effective charge concept, we can study at which laser intensity the contribution to the high-energy HHG from ${\mathrm{Ar}}^{+}$ ions precede over the Ar atoms. Comparing the HHG behavior from Ar atoms and ${\mathrm{Ar}}^{+}$ ions in the superintense laser field, we conclude that the high-energy HHG observed in the recent experiment originated from the ionized Ar atoms.