Excitation Energy Transfer

Abstract

This chapter considers the transfer of electronic excitation energy within a molecular aggregate. It explains the construction of the respective Hamiltonian in detail. The chapter discusses the coupling of electronic excitations between different molecules, which causes excitation energy delocalization and transfer, as well as the interaction with the various types of vibrational degrees of freedom. It then focuses on the so-called Frenkel exciton model, where the moving excitation energy is completely described as an intramolecular excitation, and no charge transfer between different molecules occurs. The chapter also describes excitation energy transfer (EET) in a situation of weak and strong dissipation. It demonstrates how optical absorption spectra are influenced by the formation of Frenkel exciton states. The chapter then discusses EET in terms of photon exchange, and describes the formation of charge-transfer excitons and the process of exciton–exciton annihilation.