Construction and Application of a Multi-Function Laser Photolysis ESR

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In order to make a multi functional laser photolysis ESR spectrometer by combining an ESR spectrometer with various equipments for spectroscopic measurements the followings were made.(1) A variable wavelength pulsed-TAG laser system was introduced to perform laser photolysis at various wavelengths in the visible to UV region. (2) An ESR cavity was modified to do simultaneous measurements of CIDEP and laser photlysis. (3) Simultaneous measurements of ESR,reansient absorption and fluorescence were tried using an ESR cavity. (4) The ESR spectrometer was modified to do optical detection of ESR by inducing microwave transitions among spin-sublevels. After checking the performance of the spectrometer system, the follwoing studies were made.1) Studies of the initial processes of photochemical reactions by ESR and transient absorption : We have made a detailed investigation on the CIDEP of redicals produced by hyrogen abstraction reactions of azaaromatic molecules by 2-propanol. The observed CIDEP signals are strongly dependent on the concentration, the excitation light intensity and the delay time, showing that several different CIDEP mechanisms are involved. It was concluded that the net emissive polarization observed at relatively high concentrations are likely due to the radical-triplet pair mechanism (RTPM). The time profiles of the observed signals were comparaed with the theoretical predictions made on the basis of possible reaction and relaxation schemes. The effect of the T-T annihilation on the CIDEP signal rise was also clarified.2) CW and FT time-resoved ESR studies of photochemical reactions and CIDEP : Detailed investigations on the quenching rates of various molecules by 2-propanolyl radical and the magnetic field dependence of the triplet mechanisms of CIDEP were made and much new information was obtained.