INVESTIGATION OF EXCITED-STATES OF CHLOROPHYLL IN THE LIGHT-HARVESTING COMPLEXES BY NONLINEAR ABSORPTION-SPECTROSCOPY

Excited states of pigments in the light-harvesting complexes of photos ystem II of higher plants and of purple bacteria Rb.sphaeroides were s tudied. In experiments the picosecond light pulses at the wave length of pump and probe pulses of 590 nm were used. The dependence of the tr ansmission of preparates on the intensity of excitation and kinetics o f the optical density changes ender intensive excitation were measured . The theoretical fitting of the experimental curves were done accordi ng to the model introduced by Voigt for the explanation of the same ef fects measured with nanosecond light pulses. It was concluded that the minimal structure unit of investigated pigment complexes presents the cluster al strong interacting molecules. The excitation arised in the such cluster is delocalized. Parameters characteristic for the excita tion in the pigment-protein complexes of strong interacting molecules were calculated.