Figure 1: The set-up.
(a) Geometry: molecules confined in the xy plane, perpendicular to the quantization axis z; (Rij; φij) are the polar coordinates of the vector Rij joining molecules i and j. (b) Rotational levels of a molecule. The small icons mimic the angular distributions of the rotational states and are coloured according to their phase, the arrows showing the direction of the phase winding in the |1, ±1› states. (c,d) Processes involving dipolar exchange interactions. In c, molecules exchange rotational levels while preserving both their total internal angular momentum and its z-component. In d, the internal angular momentum decreases by 2, while the orbital momentum of the two molecules increases by 2.
