Ultrafast Angular Momentum Orientation by Linearly Polarized Laser Fields

We theoretically show and experimentally verify that a pair of linearly polarized intense femtosecond pulses can create molecular ensembles with oriented rotational angular momentum on an ultrafast (approximately ps) time scale, when the delay and the mutual polarization between them are appropriately arranged. An asymmetric distribution for +M and -M sublevels relies on quantum interference between rotational wave packets created in stimulated Raman excitation by the first and second pulses. The present approach provides spatiotemporally propagating ensembles, of which the classical perspective is molecules rotating in a clockwise or counterclockwise direction.