ULTRAFAST INITIAL REACTION IN BACTERIAL PHOTOSYNTHESIS REVEALED BY FEMTOSECOND INFRARED-SPECTROSCOPY

The early temporal evolution of the transient infrared difference spec trum of bacterial reaction centers of Rhodobacter sphaeroides between 1000 and 1600 cm(-1) reveals a strong 200 fs component which has not y et been detected in femtosecond experiments in the visible or near inf rared region. A detailed analysis of the experimental data shows that this fast component can be explained by a considerable change of the e lectronic structure of the primary electron donor, the special pair, d uring this time. A possible explanation of the reaction relates this p rocess with an ultrafast initial intramolecular charge separation in t he special pair P.