Energy transfer , photosynthetic reaction applications

A microscopic theory for describing ultrafast radiationless transitions in particular for, photo-induced ultrafast radiationless transitions is presented. For this purpose, one example system that well represents the ultrafast radiationless transaction problem is considered. More specifically, bacterial photosynthetic reaction centers (RCs) are investigated for their ultrafast electronic-excitation energy transfer (EET) processes and ultrafast electron transfer (ET) processes. Several applications of the density matrix method are presented for emphasizing that the density matrix method can not only treat the dynamics due to the radiationless transitions but also deal with the population and coherence dynamics. Several rate constants of the radiationless transitions and the analytic estimation methods of those rate... 

Non-Forster fluorescence quenching of trans-etiochlorin by magnesium oc-taethylporphine in phosphatidylcholine vesicles gives evidence for a statistical pair energy trap. Energy transfer also occurs in the excited singlet manifold of chlorophyll. " The photophysics of bis(chlorophyll)-cyclophanes, models of photosynthetic reaction centres, have been explored for use in artificial photosynthesis.Picosecond time-resolved energy transfer in phycobilosomes have also been studied with a tunable laser. The effect of pH on photoreaction cycles of bacteriorhodopsin, " the fluorescence polarization spectra of cells, chromatophores, and chromatophore fractions of Rhodospirillum rubrum, and a brief review of the mechanism and application of artifical photosynthesis are all relevant to the subject of this Chapter. 

The photocatalytic properties and electron/photon-induced processes related to natural systems treated in Chapters 13 and 14 have been researched in depth. Different single fundamental multi-electron catalytic processes and photoexcited state electron-transfer reactions, both in polymer matrixes, are described in relation to photosynthesis (Section 13.2). It is now necessary to combine these reactions step by step to produce artificial photosynthetic systems. Some photoinduced energy-transfer processes (photooxidations) have now reached the level of practical application for wastewater cleaning (Section 13.4) and should be extended to other reactions induced by irradiation with visible light. 

The intensity of fluorescence from an immobilized, isotropic sample of photosynthetic reaction centers (RCs) increases upon application of an electric field at 77 K [IJ. The change in fluorescence was found to be quadratic with the applied field strength, and the fluorescence in the field was found to become polarized [2]. The fluorescence increase is ascribed to a net decrease in the rate of the forward electron transfer reaction which competes with fluorescence from P. The field alters the free energy change for electron transfer, AG, and thus the rate because the energy of the dipolar product state... 

The second article also deals with PET in arranged media, however, this time by discussing comprehensively the various types of heterogeneous devices which may control supramolecular interactions and consequently chemical reactions. Before turning to such applications, photosynthetic model systems, mainly of the triad type, are dealt with in the third contribution. Here, the natural photosynthetic electron transfer process is briefly discussed as far as it is needed as a basis for the main part, namely the description of artificial multicomponent molecules for mimicking photosynthesis. In addition to the goal to learn more about natural photosynthetic energy conversion, these model systems may also have applications, which, for example, lie in the construction of electronic devices at the molecular level. 

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