Superradiance and Exciton (De)localization in Light-Harvesting Complex II from Green Plants?

Fluorescence quantum yield and fluorescence lifetime measurements were performed on trimeric light-harvesting complex II (LHCII) from spinach in the temperature range 7−293 K. From the results the radiative rate was calculated, which is related to the amount of delocalization of excitations over different pigments because of intermolecular interactions. The emitting dipole strength of LHCII is very similar to that of unbound Chl a, and it appears to be almost independent of temperature. The apparent increase of the radiative rate upon lowering the temperature can largely be explained by the shrinking of the sample. It is concluded that at all temperatures the amount of exciton delocalizatio…