On the relation between absorption and fluorescence emission spectra of photosystems: Derivation of a Stepanov relation for pigment culsters.

Stepanov (1957a, Soviet Physics-Doklady 2: 81-84) obtained an equation which relates the absorption spectrum and the fluorescence emission spectrum of a single dye molecule. Here, a similar equation is derived for a cluster of interacting pigments, e.g. the antenna pigments of a photosystem. This relation can be used to assess the possibility of occurrence of rapid exciton equilibration (Dau and Sauer, 1996, Biochim. Biophys. Acta, 1273: 175-190). The excited state potential of a pigment cluster is discussed and compared to the excited state potential of a single pigment.