Introduction of a 60 fs deactivation channel in the photosynthetic antennaLH1 by Ni-bacteriopheophytin a

Forty femtosecond pump and probe investigations in the 870 nm absorption ba nd 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 reco very time with increasing amount of exchanged pigments. In the Ni-bacteriop heophytin 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 c onversion in Ni-bacteriopheophytin. (C) 2000 Elsevier Science B.V. All righ ts reserved.