Influence of Solvent-Solute Interactions on Molecular Dynamics

在化学系物理化学计划的这个项目中，芝加哥大学的格雷厄姆·弗莱明将在飞秒时间尺度上研究凝聚相中的化学动力学。超快光谱和非线性光谱技术将被用来探测溶液中的分子动力学，而溶液中的分子动力学通常被液体电子光谱的无特征性质所掩盖。超短脉冲将与脉冲序列相结合，以研究实验系统及其溶剂中存在的全部时间尺度。要研究的结构包括具有光合作用反应中心的生物系统。各种化学现象，如电子转移，将被合理化，并使用光谱密度进行预测。为了确定溶剂诱导曲线交叉的机理，将观察到碘解离的笼形效应。这项研究将试图发现和审视几个问题。一种是研究液体中的溶剂分子对反应的影响，试图确定，例如，在什么条件下，溶剂在反应物种周围形成笼子，并使它们足够接近，以便反应发生。这些溶剂分子是否改变了这些试剂分子的反应条件？作为生命系统特征的水溶液中的蛋白质是如何受到影响的？这些实验还将考察光合作用机制的某些方面，以更全面地了解这一重要的生命过程。

In this project in the Physical Chemistry Program of the Chemistry Division, Graham Fleming of the University of Chicago will examine chemical dynamics in condensed phases on a femtosecond time scale. Ultrafast spectroscopy and non-linear spectroscopic techniques will be used to probe the molecular dynamics in solution which are usually masked by the featureless nature of liquid-phase electronic spectra. Ultrashort pulses will be combined with pulse sequences to study the full range of time scales present in the experimental system and its solvent. Structures to be studied include biological systems with a photosynthetic reaction center. Various chemical phenomena such as electron transfer will be rationalized and predicted using spectral densities. The cage effect on the dissociation of iodine will be observed to determine the mechanism of solvent-induced curve crossing. This research will attempt to find examine several issues. One involves the effect of solvent molecules in liquid solutions on reactions in an attempt to determine, for example, under what conditions the solvents form cages around reactive species and keep them close enough for reaction to occur. Do these solvent molecules modify the reactive condition of these reagent molecules? How are proteins affected in the water solutions which are characteristic of living systems? These experiments will also examine some aspects of the mechanism of photosynthesis in order to gain a fuller understanding of this important life process.