Multidimensional Spectroscopic Studies of Condensed Phase Dynamics

有了这个奖项，化学结构、动力学和机制A项目将资助加州大学伯克利分校的格雷厄姆·弗莱明的研究，以开发两种新的实验方法来研究能量流经单个分子的方式，即使这种流动受到分子可能溶解的溶剂的影响。例如，活体组织中的分子总是被大量的水和其他物质包围着，这些物质会影响这些分子从光中吸收能量并重新分配能量的方式。水或其他溶剂的影响可能相当大，目前可用的实验技术无法将溶剂的影响从感兴趣的分子中分离出来。在这个项目中，正在开发两种新方法。第一种方法，被称为“二维电子振动光谱”，或2D-EV，将使研究人员能够直接观察光能的流动，例如，当绿色植物经历光合作用过程时。在这项工作中正在开发的第二项新技术，被称为“二维荧光检测相干光谱”，或2D-FDCS，将更直接地测量溶剂（通常是水）对感兴趣分子的影响。这项工作通过开发新设备对科学基础设施产生了广泛的影响，从而解决了从生物学到材料科学的各种问题。各个层次的学生都将参与其中，包括来自奥克兰地区当地学校的年轻学生，否则他们可能没有机会考虑从事科学事业。本项目有两个目的：(1)研究电子-振动耦合；(2)了解溶剂环境在保持量子相干性中的作用。为了实现这些目标，正在发展两种新的方法。第一种新方法是建立一种新的二维光谱技术，2D-EV，用于阐明核运动在分子和纳米材料电子动力学中的参与和作用。该技术通过将电子（可见）光谱与系统的第二维（中）红外光谱作为等待时间的函数相关联，来测量电子和振动坐标之间的相互作用。跟踪电子和振动自由度的超快时间演化的能力允许研究电子和核动力学之间的耦合，例如，在Born-Oppenheimer近似失效的势面区域，例如在发生锥形相交的情况下。通过提供位置敏感标签，该方法因此能够直接探索能量流动途径。第二项新技术，2D-FDCS，旨在将光子回波和相关技术扩展到小集合，并最终扩展到单分子。该方法可用于检测来自小集合和单分子纳米颗粒的微弱信号，并允许对波动和环境频率分布进行采样。结果是对溶剂环境在破坏量子相中的作用以及系综平均掩盖真实微观动力学的程度的新见解。该小组还使用理论方法来解释他们的实验，并为研究指明新的方向。

With this award, the Chemical Structure, Dynamics and Mechanisms A program is funding the research of Graham Fleming of the University of California Berkeley to develop two new experimental methods to study the way energy flows through individual molecules, even if that flow is affected by the solvent the molecules might be dissolved in. Molecules in living tissue, for example, are always surrounded by a great deal of water and other substances that affect the way those molecules absorb energy from light and redistribute it. The influence of the water or other solvent can be quite large, and currently available experimental techniques are unable to separate the effects of the solvent from the molecule of interest. In this project, two new methods are being developed. The first method, which is called "two dimensional electronic-vibrational spectroscopy," or 2D-EV, will enable the investigators to directly observe the flow of light energy in, for example, a green plant as it undergoes the process of photosynthesis. The second new technique being developed in this work, known as "two dimensional fluorescence-detected coherent spectroscopy," or 2D-FDCS will more directly measure the influence of the solvent (usually water) on the molecule of interest. This work is having a broad impact on scientific infrastructure through the development of new devices so solve problems ranging from biology to materials science. Students at all levels will participate, including young students from local schools in the Oakland area who might not otherwise have the opportunity to consider a career in science.This project has two aims: (1) to investigate electronic-vibrational coupling; and (2) to understand the role of the solvent environment in preserving quantum coherence. To achieve these aims, two new methodologies are being developed. The first of the new methodologies involves the construction of a new two-dimensional spectroscopic technique, 2D-EV, used to elucidate the involvement and role of nuclear motions in molecular and nanomaterial electronic dynamics. This technique measures the interplay between electronic and vibrational coordinates by correlating the electronic (visible) spectrum with a second dimension, the (mid) infrared spectrum of the system, as a function of waiting time. The ability to follow the ultrafast temporal evolution of both electronic and vibrational degrees of freedom allows the study of coupling between electronic and nuclear dynamics in, for example, regions of the potential surface where the Born-Oppenheimer approximation breaks down, such as in situations where conical intersections occur. By providing a site-sensitive tag, the method is, thus, enabling direct exploration of energy flow pathways. The second new technique, 2D-FDCS, aims to extend photon echo and related techniques to small ensembles and, eventually, single molecules. This method can be used to detect weak signals from small ensembles and single molecule nanoparticles and is allowing a sampling of fluctuations as well as the distribution of environmental frequencies. The result is new insight into the role of the solvent environment in destroying quantum phase and the degree to which the ensemble average masks the true microscopic dynamics. The group is also using theoretical methods to interpret their experiments and inform new directions for study.