Molecular Angular Momentum Alignment and Orientation Using Dressed States

In general, molecules are not spherically symmetric objects and as a result most of their interactions with other molecules, atoms, or electromagnetic fields are dependent on their spatial alignment and orientation. The ability to manipulate the rotational angular momentum of molecules makes it possible to obtain molecular frame information as well as allows control of physical and chemical processes whose rates are dependent on the orientation of the molecular axis. We have experimentally demonstrated state selective molecular angular momentum alignment and orientation using dressed states created by a cw optical field. The experiment was carried out with Li₂ molecules and combinations of linearly (alignment) or circularly (orientation) polarized lasers. Our results show that the dependence of the Rabi frequency on the quantum number M, representing the projection of angular momentum on a laboratory fixed axis, through the Autler-Townes effect, makes it possible to achieve M-state selectivity and thus molecular angular momentum alignment and orientation.