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

我们利用飞秒电子光谱、皮秒时间分辨振动光谱和泵浦探测光谱研究了凝聚态的光化学动力学，使我们能够观察到核波包的运动。主要研究成果如下：1.利用泵浦探测光谱技术研究了二苯基环丙烯的超快光解反应。观察到了S_2态的波包运动，并讨论了它与反应坐标的关系。发展了时间分辨时域拉曼光谱技术。利用这种方法，我们在时间域中观察到了反式二苯乙烯和联二异丙苯在激发态的拉曼活性低频振动。2.利用飞秒时间分辨光谱研究了7-氮杂环二聚体的光致质子转移和反式偶氮苯的光致异构化反应，并阐明了它们的反应机理。研究了绿色荧光蛋白生色团模型化合物的超快荧光动力学，讨论了其超快无辐射弛豫过程。3.利用溶剂化电子的电子跃迁，在共振条件下测量了水的皮秒时间分辨拉曼光谱。发现溶解电子的水分子产生了很强的共振拉曼散射。4.研制了荧光上转换显微镜。它首次在荧光测量中同时实现了飞秒时间分辨率和亚微米空间分辨率。发展了一种新的飞秒荧光成像技术，使我们能够观察到时间波长二维图像的荧光强度。研制了一种双光子吸收多通道检测装置。测量了视网膜和C_(60)的精密双光子吸收光谱。

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.