Femtosecond Dynamics and Phase Relaxation of Electron Transfer Reaction in Double Metal Complex Crystals

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For the tilted study, a femtosecond cavity-dumped Ti : Sapphire laser has been constructed for the first time in Japan. We have succeeded to increase a pulse energy to 10 times (35 fs, 20 nJ/pulse) with variable repetition rates(10 kHz-76 MHz) in a diffraction efficiency (40-60%). Although we have tried to measure phase relaxation signals in pump-probe measurements of double metal complex crystals and thin crystal films of photo-conducting materials such as oxotitanylphthalocyanine, we could not succeed yet to get any information of phase relaxation in pump-probe measurements at this moment. This is due to a bad s/n ratio in pump-probe measurement of present our system and some thermal problems in neat crystals. We are trying to apply this method to diluted solid systems.Energy transfer reactions in guest-doped crystals have also been investigated by means of time-correlated photon-counting consists of this laser system. In the case of highly doped Os^<2+> : [Ru(bpy)_3](PF_6)_2 crystal, the host emission decay of ^3CT(Ru) was non-exponential. The decay is ascribed to the various rate constants of energy transfer depending on the excited host-guest distances, which are changed as a result of excitation migration through the host molecules. By a stochastic simulation, rates are determined to be 1.2 x 10^<10> s^<-1> for the closest Os(II) and 3 x 10^8 s^<-1> for the excitation migration to the closest Ru(II). The mechanism of energy migration and transfer in the closest condition of metal centers are ascribed to electron exchange interaction.