Single-Active-Electron Approximation for Describing Molecules in Ultrashort Laser Pulses

A numerical approach that allows for the solution of the time-dependent Schr\"odinger equation (TDSE) describing molecules exposed to intense short laser pulses was developed. The molecular response to the strong field is described within the single-active electron approximation (SAE). The method is applied to molecular hydrogen and the validity of the SAE is investigated by comparing the ionization and electronic excitation yields to full two-electron solutions of the TDSE. The present results are also used to investigate the validity of approximate SAE methods like the molecular Ammosov-Delone-Krainov and the strong-field approximation. Finally, results for larger molecules like O$_2$, N$_2$, and C$_2$H$_2$ (acetylene) are presented.