Development of Highly Time-resolved High Frequency EPR and Application to Studies on the Excited States

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The following results were obtained for the construction of the EPR apparatus and its research applications.1. In order to increase time-resolution of the W-band EPR system, we bought a wide band amplifier, made impedance matching to 2000, and achieved a time resolution of less than 5 nano-seconds and a decrease of the loss of the signals.2. We applied this high frequency EPR machine to the studies of excited multiplet states and obtained data of excited state dynamics and spin relaxations.3. We also obtained EPR signals for the first time under a thermal equilibrium condition in the excited multiplet states of an excited triplet-radical system. Such spectra were more easily analyzed in terms of an energy difference between the multiplet states and an exchange interaction parameter J.4. The polarized spectra are now easily analyzed by using the data obtained above (under a thermal equilibrium condition) in terms of excited state dynamics and spin relaxations.5. With these data (an energy difference between the multiplet states, an exchange interaction parameter J, excited state dynamics, and spin relaxations), we succeeded in subtracting important factors which determine excited state properties in two different isomer radicals-excited triplet systems.