| Abstract
| - Exciton dynamics in the B850 and B875 bands of isolated complexes of Rhodopseudomonas acidophila(strain 10 050 and 7050) and in the B875 band of isolated complexes of Rhodobium marinum were investigatedby means of accumulated photon echo and pump−probe techniques at different temperatures and wavelengths.For all three systems, the optical dephasing time T2 was found to be very similar: at 4.2 K, T2 is 116 and 106ps for the B850 and B875 bands of Rhodopseudomonas acidophila, respectively, and 93 ps for the B875band of Rhodobium marinum. The rapid dephasing, which displays glassy character, is a consequence of thestrong pigment−protein interactions that arise through the rather short distances in these complexes. Theobserved dephasing time at the red edge of the B850 band of Rhodopseudomonas acidophila at 4.2 K revealsthe existence of spectral diffusion in this system. From the wavelength dependence of the pump−probe signalin the B875 LH1 band of Rhodopseudomonas acidophila at 3 K it is concluded that energy transfer betweenenergetically inequivalent LH1 rings occurs on a time scale of several tens picoseconds, while energy trappingtakes place in about 250 ps.
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