SPECTRAL HOLE-BURNING IN PIGMENT-PROTEIN COMPLEXES OF PHOTOSYNTHETIC BACTERIA

The excited-state dynamics of the peripheral light-harvesting complex LH2 (B800-850) of Rb. sphaeroides is compared to that of the dimer sub unit (B8200(OG)) of the core antenna complex LH1 of Rs. rubrum G9 at l iquid helium temperatures by means of spectral hole burning. Both the B800 band of the LH2 complex and the absorption band of the B820(OG) s ubunit are inhomogeneously broadened. The homogeneous line width, GAMM A(hom), of B800 is determined by energy transfer within the LH2 comple x (tau(transfer almost-equal-to 0.8 to 2.5 ps); it is temperature inde pendent between 1.2 and 30 K and a factor of about 60 larger than that of B820(OG). By contrast, for B820(OG) GAMMA(hom) is only approximate ly 1 GHz at 1.2 K; it depends on temperature and is predominantly give n by pure dephasing.