Alignment-Dependent Strong Field Ionization of Molecules

We demonstrate a method to measure strong field laser ionization of aligned molecules. The method employs a macroscopic field-free dynamic alignment, which occurs during revivals of rotational wave packets produced by a femtosecond laser pulse. We investigate the dependence of strong field ionization of ${\mathrm{N}}_{\mathrm{2}}$ on molecular orientation. We determine that ${\mathrm{N}}_{\mathrm{2}}$ molecules are four times more likely to ionize when aligned parallel to the field than when aligned perpendicular to it.