2004 Volume 77 Issue 12 Pages 2173-2178
By using transient absorption and photoconductivity measurement techniques, we have investigated the photoionization process of N,N-diethyl-p-phenylenediamine in various polar solvents. Significant excitation wavelength and excitation intensity effects were observed in alcoholic solvents. The slowly rising component of the photoconductivity in hundreds of nanoseconds or longer time scale is ascribed to the dissociation of the monophotonically produced ion pairs. In addition, a photoconductivity signal that has almost the same duration as the excitation laser pulse and is due to the geminate pair formed via the two-photon ionization is clearly observed with the 248-nm excitation. On the other hand, the biphotonic process was negligible with the 351-nm excitation in ethanol and 1-propanol. The monophotonically formed long-lived ion pair did not contribute to the conductivity. The long lifetime of the ion pair indicates that not only the Coulombic interaction but also the exciplex-like specific interaction is important.
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