State-Resolved Spectroscopy and Dynamics of Chemical Transients

该奖项由化学学部化学结构、动力学和机制项目资助，来自JILA/科罗拉多大学的David J. Nesbitt教授将使用最先进的化学物理方法来研究涉及高活性分子瞬态的基本问题，范围从海洋边界的大气化学到星际介质中的化学。这个实验项目的总体目标有三个：i)开发高灵敏度直接吸收红外激光方法，用于研究狭缝超音速放电扩展中的基本射流冷却分子离子、分子簇和分子离子簇；ii)开发和实施新的光谱工具，用于气体-离子溶液和气体-液体微射流界面的量子态分辨碰撞研究；iii)利用时间分辨荧光显微镜和激光“纳米浴缸”加热方法的强大组合，在单分子水平上对温度和粘度依赖的RNA折叠/展开进行基础化学物理研究。分子相互作用形成液体或固体的方式通常是由相对较弱的力驱动的，这可以通过这些物质的小簇的激光光谱来详细研究。类似地，这些光谱工具也可以扩展到探测在气液界面碰撞的分子的相互作用，特别是研究它们在上层液体层溶解的概率，以及它们简单地“反弹”回气相的频率。在一个非常真实的意义上，这些研究允许人们询问气液界面上分子的化学组成。最后，我们已经建立了一种仪器，可以将显微镜镜头中的激光脉冲聚焦到足够小的光斑大小，以照亮带有第二个荧光标记（即受体）的双标记RNA生物分子中的单个荧光标记（即供体）。通过监测光的颜色、时间和偏振，我们可以了解到两种染料标签的接近程度，这使我们能够实时观察（即毫秒到秒到分钟），例如，从单链形成双链DNA的动力学，或者将单个蛋白质折叠成一个有活性的酶活性结构。这项工作将有助于培养化学物理高级领域（如量子光学、激光、等离子体和电子学）的研究生和本科生，同时进一步发现新的基础研究知识。这些研究的结果将为学生提供参与全国专业会议的机会，通过科学开放日进行推广，与当地高中进行指导，以及为中小学生提供“CU奇才”科学推广计划。

Through this award, funded by the Chemical Structure, Dynamics, and Mechanisms Program of the Division of Chemistry, Prof. David J. Nesbitt from JILA/University of Colorado will use state-of-the-art chemical physics methods to investigate fundamental problems involving highly reactive molecular transients, ranging from atmospheric chemistry at the marine boundary to chemistry in the interstellar medium. The overall goals of this experimental program are threefold: i) exploit high sensitivity direct absorption IR laser methods for study of fundamental jet cooled molecular ions, clusters and molecular ion clusters in slit supersonic discharge expansions, ii) develop and implement novel spectroscopic tools for quantum state-resolved collision studies at gas-ionic solution and gas-liquid microjet interfaces, and iii) utilize the powerful combination of time resolved fluorescence microscopy and laser "nanobathtub" heating methods for fundamental chemical physics studies of temperature and viscosity dependent RNA folding/unfolding at the single molecule level.The way molecules interact to form a liquid or a solid is generally driven by relatively weak forces, which can be studied in detail by laser spectroscopy of small clusters of these species. In a similar vein, these spectroscopic tools can also be extended to probe the interactions of molecules colliding at the gas-liquid interface, specifically investigating with what probability they dissolve in the top liquid layer and how often they simply "bounce" back into the gas phase. In a very real sense, these studies permit one to interrogate the chemical composition of the molecules at the gas-liquid interface. Finally, we have built instruments that can focus laser pulses in a microscope lens down to a small enough spot size to illuminate a single fluorescent label (i.e., the Donor) in a doubly labeled RNA biomolecule with a second fluorescent label (i.e., the Acceptor). By monitoring the color, time, and polarization of the light that gets reemitted, we can learn about the proximity of the two dye labels, which allows us to watch in real time (i.e., msec to sec to minutes), for example, the kinetics for forming double stranded DNA from single strands, or the folding of a single protein into a competent, enzymatically active structure. This work will enable the training of graduate and undergraduate students in advanced areas of chemical physics (e.g., quantum optics, lasers, plasmas, and electronics), while furthering the discovery of fundamental new research knowledge. The results of these studies will provide opportunities for student participation in national professional meetings, outreach through scientific open houses, mentoring with the local high schools, as well as operation of the "CU Wizards" Science Outreach Program for elementary and middle school students.