Real-time observation and control of the condensed-phase photochemical dynamics using optimized ultrashort optical pulses

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We studied photochemical dynamics in the condensed phase by using femtosecond electronic spectroscopy, picosecond time-resolved vibrational spectroscopy, and pump-probe spectroscopy that enables us to observe nuclear wavepacket motions. Major outcomes are followings.1.Ultrafast photodissociation of diphenylcyclopropenone was studied by pump-probe spectroscopy based on 10-fs pulses. The wavepacket motion of the S_2 state was observed, and its relevance to the reaction coordinate was discussed. Time-resolved time-domain Raman spectroscopy was developed. With this method, we observed Raman-active low-frequency vibrations of trans-stilbene and binapthyl in the excited state in the time domain.2.Photo-induced proton transfer of the 7-azaindole dimer and photoisomerization of trans-azobenzene were studied by femtosecond time-resolved spectroscopy, and their reaction mechanisms were clarified. Ultrafast fluorescence dynamics of a model compound of chromophore of Green Fluorescence Protein was investigated, and its ultrafast radiationless relaxation process was discussed.3.Picosecond time-resolved Raman spectra of water were measured under the resonance condition with the electronic transition of the solvated electron. It was discovered that the water molecules that solvate the electron give rise to strong resonance Raman scattering.4.Fluorescence up-conversion microscope was developed. It simultaneously achieved femtosecond time-resolution and sub-micron space-resolution in fluorescence measurements for the first time. A new femtosecond fluorescence imaging technique was developed, which enabled us to observe fluorescence intensity as a time-wavelength two-dimensional image. An apparatus for multi-channel detection of two-photon absorption was developed. Precise two photon absorption spectra of retinal and C_<60> were measured.