Femtosecond laser pulse shaping for enhanced ionization

We demonstrate how the shape of femtosecond laser pulses can be tailored in order to obtain maximal ionization of atoms or molecules. For that purpose, we have overlayed a direct-optimization scheme on top of a fully unconstrained computation of the three-dimensional time-dependent Schrodinger equation. The procedure looks for pulses that maintain the same total length and integrated intensity or fluence as a given pulse that serves as an initial guess. It allows, however, for changes in frequencies -- within a certain, predefined range -- and overall shape, leading to enhanced ionization. We illustrate the scheme by calculating ionization yields for the H2+ molecule when irradiated with short (~5 fs), high-intensity laser pulses.