High-frequency time-resolved EPR Study on the Short-lived Paramagnetic Species

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We built a Q-band time-resolved EPR spectrometer, which works with a pulsed laser. We applied the system to verify the mechanism of the ClDEP spectra due to short-lived radicals and the broadening mechanism of the time-resolved EPR spectra due to short-lived excited triplet states.1. Microwave frequency dependence of spin-polarized EPR spectra(a) The CIDEP spectra involving triplet mechanism depends on significantly to the observed frequency.(b) Time-resolved EPR measurements on the excited triplet states verified that the spectral broadening due to the g-anisotropy is clearly distinguished from the other mechanisms.2. The sign of the exchange interaction in the radical ion pairs.The present study verified that the exchange interaction is governed by charge transfer interaction rather than covalent bonding interactions, The level crossing between the potential surfaces of the radical ion pair state and ground state is a key factor.3. Electronic structure of the excited state of diphenyl carben.We successfully observed the short-lived excited state of diphenylmethylene and determined the zero-field splitting constants.4. Structure of the dangling bonds in microcrystalline silicon.Q-band EPR measurements verified the existence of three kinds of signals due to dangling bonds in microcrystalline silicon.5. Eelctronic structure of the excited triplet states having unusually large zero-field splitting constants.