The Ultrafast Energy Transfer Process in Purple Bacteria Photosynthetic Reaction Center

The ultrafast energy transfer process, which takes place in femtosecond time range, in bacterial photosynthetic reaction center RS601 was investigated using femtosecond pump-probe technique with selective excitation. Upon 755 nmexcitation, the excited state of bacteriopheophytin H decayed to bacteriochlorophyll B with a time constant of about 130 fs, while the excited state of B transported the energy to its energy acceptor, the dimeric bacteriochlorophyll P, in about 240 fs with the 800 nm excitation. The internal conversion process between the upper and lower exciton levels of special pair P might exist upon the excitation of 850 nm pulses. In addition, from the results obtained in our experiments, the charge separation and electron transfer from P to the acceptor H was also observed via the real intermediate B within a few picoseconds.