A VIEW OF FAST CHARGE SEPARATION IN THE BACTERIAL PHOTOSYNTHETIC REACTION CENTER INVOLVING WEAK ENVIRONMENTAL DAMPING OF A POPULATED AUXILIARY CHLOROPHYLL STATE

The initial fast electrical charge separation in the bacterial photosy nthetic reaction centre involves electron transfer (ET) from the photo -excited special pair chlorophyll to pheophytin. The ET is assisted by the auxiliary chlorophyll monomer which may be populated in the sub-p icosecond time range. We provide a new theoretical description of this process which rests on three-level coherent ET theory, incorporating environmental damping and partial vibrational relaxation in the interm ediate state of auxiliary chlorophyll population. If damping is not to o strong, this view offers a clue to the ultrafast, activationless and possibly coherent character of both steps, also in the limit when the electronic coupling between the three molecular entities is weak.