Chirality in fluorescence and energy transfer

The optical polarization features associated with the fundamental processes of molecular fluorescence and resonance energy transfer are in general studied with reference to plane polarizations. When any of the species involved is chiral, the associated emission processes can exhibit an element of circular polarization – a degree of optical ellipticity. Although this is usually a minor effect, some systems can exhibit a sizeable component of circularly polarized luminescence, whose helicity correlates with enantiomeric form. In cases where energy transfer leads to emission from an achiral acceptor, the helicity in the emission is in fact governed by the handedness of a chiral donor, leading to some speculation on a mechanism that might 'convey' chirality. Casting the fundamental theory in terms of the formal electrodynamics enables the symmetry principles and the quantum mechanisms involved in such phenomena to be understood. The results can provide fresh physical insights, and establish connections across a range of indirectly related chiroptical phenomena including induced circular dichroism.