Effects of electric field and magnetic field on photoinduced dynamics and the role of molecular orientation

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External electric firld effects on the initial step of the elctron transfer process, charge recombination process and charge dissociation process have been examined in various types of photoinduced electron transfer wtytem composed of donor and acceptor doped in a PMMA polymer film by measuring the elctric field effects on absorption and fluorescence spectra. The filed effect has been also examined in methylene-linked compounds of donor-acceptor system. As a result, the rate of the photoinduced electron transfer was found to be enhanced by an electric field. The charge recombination process as well as the charge dissociation process was also found to be affected by an electric field. In methylene-lined compounds of carbazole and terephthalic acid, further, the field-induced inhibition of the charge recombination was found to depend markedly on the methylene chain length.Electron donor and acceptor layrs separated by a spacer layr were also prepared with a cyanine dye and viologen using the Langmuir-Blodgett technique, and the effect of an external electric field on the initial step of the photoinduced electron transfer has been examined on the basis of the measurements of the field effect on the fluorescence quantum yield of the cyanine dye. Interlayr electron transfer from the photoexcited molecules of cyanine dyes to viologen was found to be deptressed or enhanced by an external electric field, depending the direction of applied electric field.Electric dipole moment and molecular polarizability of molecular intermediates produced by photochemical reaction such as an electron transfer have been evaluated from the electrofluorescence spectra of these transient species.Besides the electron transfer process, other photochemical processes, e.g., excimer formation process of pyrene, were also found to be affected by an electric field.