ABSTRACT
In a crystal of identical chromophores, for example, a naphthalene crystal, local excitations may be transferred to other sites, just like electrons or holes. Excitation energy transfer (EET) is also called electron-hole pair transfer because the excited electron and remaining hole are transferred simultaneously to the other atom or molecule. Degeneracy appears in a ›nite system with two identical chromophores. In a repetitive system, the excitations may be delocalized, but this is not always the case. Devices for solar light harvesting, and natural antenna systems are examples of such repetitive systems. It is important to understand their properties.
