Introduction of a 60 fs deactivation channel in the photosynthetic antenna LH1 by Ni-bacteriopheophytin a

Forty femtosecond pump and probe investigations in the 870 nm absorption band of the reconstituted core antenna, LH1, from Rhodobacter sphaeroides, in which varying amounts of Ni– bacteriopheophytin replace part of the native bacteriochlorophyll, show a tremendous shortening of the ground state recovery time with increasing amount of exchanged pigments. In the Ni–bacteriopheophytin containing antenna, a 60 fs deactivation channel has been found, which originates from a one-exciton state delocalized over the whole LH1 of about 20 pigment molecules. The 60 fs channel is interpreted as internal conversion in Ni–bacteriopheophytin.