Nonlinear Optical Studies of Condensed Phase Dynamics

加州大学的格雷厄姆·弗莱明得到了实验物理化学计划的支持，继续他在复杂凝聚相系统中的动力学实验研究。 超快共振和非共振光谱学将被用来实现更好地理解电子相互作用和电子-声子相互作用的多发色团系统，特别是探测轨道混合和电子相干性的实验方法的发展。 具体计划包括将共振光子回波光谱扩展到更复杂的系统，如反应系统，蛋白质和光学活性聚合物，如树枝状光捕获复合物和导电聚合物。 此外，非极性溶剂化的机制将进行探讨。 在另一个项目中，二维拉曼光谱学将用于阐明不同核运动之间的耦合机制。将寻求对这种技术的增强，包括使用偏振来增强对信号的相对贡献，以实现从二维数据中检索结构信息的能力。 许多重要的化学和生物过程发生在溶液中，其中感兴趣的物种被大量的溶剂分子完全包围。 溶液中分子运动的快速时间尺度使这些过程适合于用超快激光技术进行探索。 理论和实验已经发展到现在可以有效地研究有用的复杂系统的程度。这些研究的结果预计将影响对生物系统中溶液现象的理解，包括蛋白质的折叠和展开转变。

Graham Fleming at the University of California is supported by the Experimental Physical Chemistry Program to continue his experimental studies of dynamics in complex condensed phase systems. Ultrafast resonant and non-resonant spectroscopy will be used to achieve an improved understanding of electronic interactions and electronic-phonon interactions in multichromophore systems, in particular the development of experimental methods that probe orbital mixing and electronic coherence. Specific plans include the extension of resonant photon echo spectroscopy to more complex systems such as reacting systems, proteins, and optically active polymers such as dendrimeric light harvesting complexes and conducting polymers. As well, the mechanisms of nonpolar solvation will be explored. In another project, two-dimensional Raman spectroscopy will be used to clarify coupling mechanisms between different nuclear motions. Enhancements to this technique, including the use of polarization to enhance relative contributions to the signal, will be sought to achieve the capability to retrieve structural information from the two-dimensional data. Many important chemical and biological processes occur in solution, where the species of interest are surrounded completely by large numbers of solvent molecules. The rapid time scales of molecular motion in solution make these processes amenable to exploration by ultrafast laser techniques. Theory and experiment have evolved to the extent that useful complex systems can now be studied effectively. Outcomes from these studies are expected to impact the understanding of solution phenomena in biological systems, including folding and unfolding transitions in proteins.