Triplet States Studied by Two-Color Excitation Time-Resolved ESR

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In this research project, we have carried out four projects using time resolved ESR technique. Results obtained are summarized as follows.(1) Energy Transfer to Higher Triplet State: It is quite difficult to know by the conventional optical spectroscopy what kind of triplet state of energy acceptor is produced in triplet-triplet energy transfer. However, we succeeded to me sure the energy transfer to higher triplet state(T_2) by the time-resolved ESR and to determine the T_2 energy.(2) Spin Polarization Transfer in the Triplet-Doublet Systems: Mechanism of spin polarization transfer was studied in the triplet-doublet systems Using relatively stable radicals as doublet sources. Since the spin polarization transfer occurred when the triplet energy was higher than the excitation energy of radicals, it is. concluded that the spin polarization transfer accompanies energy transfer.(3) Inversion of Spin Polarization in Benzil and alpha-Naphthil:CIDEP generated in the reactions benzil and alpha-naphthyl with aniline and phenol was inverted with time. This is explained by the inversion of spin polarization in the triplet state which is caused by the structural change from non-planar to planar one.(4) Photodissociation of 1-Naphthylmethylchloride: CIDEP spectra of 1-naphthylmethyl radicals was obtained by direct photoexcitation and triplet sensitized reactions of 1-naphthylmethylchloride. It is known from the analysis of CIDEP patterns that 1-naphthylmethylehloride decomposes from the low vibrational level of the lowest triplet state to yield 1-naphthylmethyl radicals and chlorine atoms.