Chlorophyll <i>a</i> Franck−Condon Factors and Excitation Energy Transfer

Abstract

The Franck−Condon factors for the S1(Qy) ↔ S0 electronic transition of chlorophyll (Chl) molecules are important for understanding excitation energy transfer in photosynthetic complexes. Currently, there are two sets of Chl a Franck−Condon factors for over 40 modes, one determined by spectral hole burning and the other by fluorescence line narrowing. Those obtained by the latter spectroscopy are, on average, a factor of 30 times smaller than the hole burning values. Nonline-narrowed fluorescence results for the light-harvesting complex II of photosystem II at 4.2 K are presented that agree quite well with the hole burning but not the fluorescence line narrowing values.