| Abstract: | Abstract. In this paper we review picosecond fluorescence studies of exciton dynamics in photosynthesis. We discuss some of the exciton interactions that led to artifacts in early picosecond data and outline procedures for avoiding their presence. In the case of high intensity single pulse excitation (> 1013 photons cm2), the dominant mechanism is singlet-singlet fusion, manifesting itself by a decrease in the observed lifetime and quantum efficiency of fluorescence. The manner in which excitons interact in vivo provides an indicator of the topology of the photosynthetic unit (PSU). The shape of the fluorescence quenching curve, as a function of intensity, in particular, can be used to test various models. In addition to fluorescence quenching curves, we also report the results of fluorescence decay following ps laser flashes, using an ultrafast streak camera in four types of systems: (1) organic crystal anologues, (2) chromatophores of various mutants of the photosynthetic bacteria, Rhodopseudomonas sphaeroides, (3) intact cells of the green alga, Chlorella and (4) chloroplasts of higher plants (e.g. spinach). |
