Estimation of the rate of photochemical charge separation in Rhodopseudomonas sphaeroides reaction centers by fluorescence and absorption picosecond spectroscopy

Time-resolved fluorometry of reaction center (RC) preparations from Rhodopseudomonas sphaeroides, wild strain 1760-1, shows that the lifetime of the excited state of bacteriochlorophyll P870 ∗ is τ = 6± 1.5 ps and independent of temperature within the range 293 – 77 K. This value was found to coincide well with the time (7 ± 3 ps) of the RC porphyrin pigment transition into the ion-radical pair state P F, as measured by picosecond absorption spectroscopy of the same preparations.