Controlling electronic energy transfer: A systematic framework of theory

The transport of electronic excitation energy (EET) between ions, atoms, molecules or chromophores is an important process that occurs in a wide range of physical systems. The tantalising prospect of effective experimental control over such transfer is, in principle, amenable to a variety of different kinds of approach. Several of the most promising, which are analysed and compared in this paper, involve the influence of externally applied static electric or electromagnetic fields, or the exploitation of local media effects. A quantum electrodynamical framework is used as a common basis to describe the corresponding mechanisms, illustrated by specially adapted Feynman diagrams. It becomes evident that energy transfer between polar species engages an additional pairwise interaction beyond the EET coupling. Such an effect may also play an important role in interatomic Coulombic decay (ICD), a process that has recently attracted fresh interest. The control of ICD, in which the photoionisation of two nearby atoms via energy transfer, is determined to have analogous characteristics to conventional forms of EET.