Laser-induced substructures in above-threshold-ionization spectra from intense few-cycle laser pulses

Abstract

We have calculated above-threshold-ionization (ATI) spectra for argon in a strong, few-cycle 400 nm laser pulse with an ab initio solution of the time-dependent Schr\"odinger equation and by using a model based on the strong field approximation. We find additional peaks in the resulting ATI spectra which are not present for longer pulses. This substructure is due to the rapidly changing ponderomotive potential in the short laser pulse. It is sensitive to the pulse duration and the pulse envelope and is a general feature of ionization spectra originating from a short, intense laser pulse.