Picosecond dynamics of excitons in mesoscopic pigment aggregates of photosynthetic proteins

Publisher Website
Google Scholar
Abstract
Population relaxation of Frenkel excitons in a natural photosynthetic light‐harvesting pigment‐protein complex (FMO protein: aggregate of 21 bacteriochlorophyll a molecules, hold together by a protein backbone) has been studied by ps fluorescence emission decay as a function of temperature between 5 K and 300 K. At low temperatures a gradual slowing down of relaxation rates was observed (from ps−1 to about ns−1) when recording at lower energies. At higher energies the rates were instrument‐limited. The dependence of relaxation rates on recording wavelength was smeared out at temperatures ≥100 K. The relatively slow rates are probably due to low density of exciton states and/or to specific coupling to vibrational modes. A strong thermally induced quenching of fluorescence intensity was observed from about 20 K. This leads to a short (<100 ps) fluorescence lifetime, measured at the band maximum at room temperature, compared to 1.1 ns at 5 K.

This publication has 0 references indexed in Scilit: