The Photo-ionization of Molecules in Solutions. III. Photo-ionization and Recombination Processes of N,N,N′,N′-Tetramethyl-p-phenylenediamine in Various Organic Solvent

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Abstract
Flash photolysis studies of N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD) were made in various solvents at room temperature. The transient absorption spectrum of the cation, TMPD+ , was observed in polar solvents. The transient was also observed in a viscous, non-polar solvent. It has a spectrum different from that of TMPD+ . Its absorbance is proportional to the flash-light intensity, and it decays exponentially, with τe=82 μ sec. This absorption is attributed to the triplet-triplet transition of TMPD. With aerated solutions, no transient spectrum was observed. The fluorescence and the phosphorescence of TMPD caused by direct excitation were investigated, together with those induced by the recombination of electrons and TMPD+ in non-polar matrices stimulated either thermally or by infrared light. The absorption spectra of TMPD in a non-polar matrix at a low temperature were investigated by means of the cross-illumination method, and the time dependence of the absorption was followed. The ionization and the recombination processes were then discussed by the use of these results.