Resonance Raman Studies of Excited-State Structure and Dynamics

在化学系物理化学计划的这个项目中，加州大学伯克利分校的Richard A.Mathies教授将进行一系列研究，以确定凝聚相光化学反应和光生物反应中发生的基态和激发态核动力学和结构变化，从而了解它们的分子反应机制。通过测量和分析绝对激光共振拉曼振动散射强度，可以确定在光化学激活系统激发后立即发生的特定模式的核动力学。皮秒时间分辨共振拉曼光谱和吸收光谱将用于研究基态光产物的形成动力学和基态光化学中间体的结构和弛豫。将进行以下研究。1)环多烯的光化学开环、闭环和1，7氢转移反应；2)细菌视紫红质和藻胆蛋白中蛋白质环境对其结合的发色基团的电子激发/光异构化的响应；3)视觉色素视紫红质的光激发；4)细菌光合作用反应中心的光化学电子转移反应；5)植物感光色素光敏色素中四吡咯生色团的光化学激发机理。这些研究探索了光和光生物活性物质之间相互作用的基础，并将有助于我们理解发生在有生命和无生命的生命系统中的基本过程。这项研究的总体目标是寻找常温下凝聚相光化学体系中化学反应发生的一般规律。

In this project in the Physical Chemistry Program of the Chemistry Division, Professor Richard A. Mathies of the University of California at Berkeley will conduct a series of investigations to determine the ground and excited-state nuclear dynamics and structural changes that occur in condensed phase photochemical and photobiological reactions and thereby understand their molecular reaction mechanisms. The mode-specific nuclear dynamics that occur immediately after excitation of a photochemically active system will be determined by measuring and analyzing absolute laser resonance Raman vibrational scattering intensities. Picosecond time-resolved resonance Raman and absorption spectroscopy will be used to study the kinetics of ground-state photoproduct formation and the structures and relaxation of ground-state photochemical intermediates. The following studies will be pursued. 1) Photochemical ring-opening, ring-closing and 1,7 hydrogen shift reactions of cyclic polyenes; 2) the response of protein environment in bacteriorhodopsin and in phycobiliproteins to the electronic excitation/photoisomerization of their bound chromophoric prosthetic groups will be studied; 3) the photoexcitation of visual pigment rhodopsin will be investigated; 4) the photochemical electron transfer reaction in bacterial photosynthetic reaction centers, and 5) the mechanism of photochemical excitation of tetrapyrrole chromophore in phytochrome, the light sensing pigment in plants, will be examined. These investigations probe the basics of the interaction between light and photo-biologically active materials and will contribute to our understanding of the fundamental processes which take place in animate and inanimate living systems. The overall goal of this research is to find general principles about how chemical reactions occur in condensed phase photochemical systems at room temperature.