Understanding the Structure and Dynamics of Solvated Electrons Using Ultrafast Spectroscopy and Quantum Simulation Methods

在这个由化学部门化学结构、动力学和机理a项目（CSDM-A）资助的项目中，加州大学洛杉矶分校的Benjamin J. Schwartz教授和他的学生正在使用实验和理论技术相结合的方法来解开溶剂化电子的结构和行为。盐水是一种常见的电解质，它含有溶解的带正电的阳离子（钠，Na+）和负电的阴离子（氯，Cl-）。在某些情况下，电子（e-）有可能溶解在液体中。这样的解决方案更难理解和预测，因为电子的质量比原子和分子小几千倍，而且更容易移动。施瓦茨小组正在使用激光产生极短的光脉冲（30 - 40千万亿分之一秒）来捕捉这些快速移动的电子的运动和能量。实验结果正在与量子力学计算（量子力学是一种处理极其微小的物体，如电子、原子和分子的数学）和计算机模拟“溶剂化”电子的液体分子的运动进行比较。这项工作的广泛影响包括更好地理解辐射化学（与溶剂化电子的反应使高能量辐射对生物体构成危险）和电子转移反应（如生物学和电池中的反应）。由于这个项目结合了实验和理论，本科生和研究生的研究人员在实验化学、激光技术和计算机编程方面获得了丰富的经验，所有这些对现代科学工作者来说都越来越有价值。施瓦茨小组还与洛杉矶地区的高中教师合作，通过讲座和实验教材的开发来丰富他们的科学课程。该项目的实验重点是利用超快光谱来研究溶剂化电子的性质。超快光谱学利用极短的光脉冲（~几十飞秒），提供了一种在室温液体中分子运动的时间尺度上“停止电子运动”的方法。该项目的理论重点是基于混合量子/经典模拟。在这里，量子力学被用来描述溶剂化电子的性质，但溶剂分子被经典地处理。模拟可以用来计算超快光谱实验的结果，因此，实验和模拟的结合可以为这种有趣而重要的化学物质的结构和反应性提供新的见解。由于溶剂化电子只涉及单个电子的运动，它们也提供了一个测试系统，可以直接将量子力学模拟的预测与实验室实验的结果进行比较。除了培训本科生和研究生，施瓦茨小组还与洛杉矶地区的高中教师合作，通过讲座和开发实验包来丰富他们的科学课程。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

In this project funded by the Chemical Structure, Dynamics and Mechanisms-A Program (CSDM-A) of the Chemistry Division, Professor Benjamin J. Schwartz and his students at the University of California-Los Angeles are using a combination of experimental and theoretical techniques to unravel the structure and behavior of solvated electrons. Salt water is a common example of an electrolyte, which contains dissolved positively charged cations (sodium, Na+) and negatively anions (chloride, Cl-). Under certain circumstances, it is possible for electrons (e-) to be dissolved in a liquid. Such solutions are more difficult to understand and predict, because electrons are thousands of times less massive than atoms and molecules, and are much more mobile. The Schwartz group is using lasers which produce extremely short pulses of light (30 - 40 quadrillionths of a second) to capture the motions and energies of these fast moving electrons. The experimental results are being compared with quantum mechanical calculations (quantum mechanics is a type of math that deals with extremely small objects like electrons, atoms, and molecules), and computer simulations of the motions of the liquid molecules that "solvate" the electron. The broader impacts of this work include a better understanding of radiation chemistry (reactions with solvated electrons make high energy radiation dangerous to living organisms) and electron transfer reactions (such as those in both biology and batteries). Because this project combines experiment and theory, undergraduate and graduate student researchers receive a rich experience in experimental chemistry, laser technology, and computer programming, all of which are increasingly valuable for the modern science workforce. The Schwartz group also works with high school teachers in the Los Angeles area to enrich their science classes through lectures and the development of experimental lesson kits.The experimental focus of the project uses ultrafast spectroscopy to study the properties of solvated electrons. Ultrafast spectroscopy takes advantages of pulses of light that are extremely short (~tens of femtoseconds), providing a means to "stop the motion" of the electrons on the time scale with which molecules move in room temperature liquids. The theoretical focus of the project is based on mixed quantum/classical simulations. Here, quantum mechanics is used to describe the properties of the solvated electrons, but the solvent molecules are treated classically. The simulations can be used to calculate the results of the ultrafast spectroscopy experiments, so that together, the combination of experiments and simulations can provide new insights into the structure and reactivity of this interesting and important chemical species. Because solvated electrons involve motions of only a single electron, they also provide a test system to compare the predictions of quantum mechanical simulations directly with the results of laboratory experiments. In addition to the training of undergraduate and graduate students, the Schwartz group also works with high school teachers in the Los Angeles area to enrich their science classes, through lectures and the development of experiment kits.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.