Principles of Directed Electronic Energy Transfer

Abstract

On the optical irradiation of a complex absorptive medium, an ultrafast transfer of electronicenergy between chromophores or sites generally takes place, preceding any ensuing fluorescence. Such transferprocesses represent a redistribution of optically acquired energy and commonly lead to the indirectexcitation of other chromophore units. Consequently, electronic energy transfer is a major determinantof detail in the fluorescence spectrum of the system. Where a sequence of energy transfer steps canbe identified, the overall directionality of each sequence is important in determining any localizationof the electronic energy. It is therefore highly significant that it is possible to exercise directionalcontrol over energy transfer, not only through the operation of an intrinsic spectroscopic gradient, butalso by a variety of less well-known methods involving applied electrical or optical fields. Exploitationof the latter methods holds promise for advances in a wide range of technologies including opticalswitching and the production of energy harvesting materials.