Theory of Rotational Orientation of Molecular Chromophores by Circularly Polarized Optical Pumping

The feasibility of creating unidirectional rotational motion of molecular or nanoscale symmetric top rotors by absorption of circularly polarized light was theoretically investigated using a stochastic Monte Carlo type simulation method. The degree of rotational orientation possible was studied as a function of the shape of the rotor chromosphere, the internal location of its transition dipole, and the probability of collisional thermalization of rotation. The polarized uorescence from the resulting rotational alignment is simulated to explore its utility as an experimental probe of the optical pumping process. The simulations show that all shapes of symmetric top rotors achieve a high degree of rotational alignment for su ciently low collision probability. In selecting molecules for experimental study of this e ect, the transition type is important in optimizing the uorescence anisotropy