Single-active-electron approximation for describing molecules in ultrashort laser pulses and its application to molecular hydrogen

A numerical approach that allows for the solution of the time-dependent Schrodinger 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 in the fixed-nuclei approximation to molecular hydrogen with parallel orientation of the internuclear axis to the laser field. 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.