Molecular reorientation in intense femtosecond laser fields

A femtosecond double-pulse experiment shows that molecular reorientation during multiple ionization is a very fast process for light molecules such as O₂ or N₂O using 60-fs laser pulses and variable time delays between ±1 ps in the 10¹⁵ W/cm² intensity range. A unified two-dimensional model of molecular multiple ionization allows one to get the multicharged fragment trajectories and consequently discuss the speed of alignment of a molecule. The numerical results confirm that the molecular reorientation process is faster when the laser intensity increases, in good agreement with the experimental data.