General theory of circularly polarized emission and magnetic circularly polarized emission from molecular systems

A theory of circularly polarized emission (CPE) based on the formalism and methods of quantum electrodynamics is developed for chiral luminescent molecular systems and for achiral luminescent molecular systems placed in a magnetic field. Differential transition probabilities for the (spontaneous) emission of left- and right-circularly polarized light are calculated and these quantities are related to the observables of CPE spectroscopy. The influence of photoselection and reorientational relaxation (due to rotary Brownian motion) upon the CPE observables (with and without an applied magnetic field) is considered. Expressions for emission anisotropy factors are derived and these factors are related to the molecular transition integrals which determine the CPE and total emission intensities. Results are obtained for two excitation–emission geometries—180° (head on) and 90° (right angle).