Investigations of Concentrated Salt and Acid Solutions Using Ultrafast Nonlinear Spectroscopy

在化学系化学结构、动力学和机制-A（CSDM-A）项目的支持下，斯坦福大学的Michael Fayer教授正在开发复杂的超快光谱，以研究溶剂化离子和质子的动力学和结构。盐和酸溶液在自然界中很常见，在技术应用中很重要。直接研究水中离子的挑战在于，离子/水动力学发生在极短的时间尺度上，万亿分之一秒，或比相机快门速度快十亿倍。Fayer教授和他的学生将推进超快红外和可见光谱方法，并使用它们来研究浓盐和酸溶液。他们的发现将增强重要离子/水系统的基础知识，并导致更好地了解复杂电解质，例如那些正在开发用于储能电池的电解质。除了通过与学术界、政府实验室和工业界共享信息和技术产生直接的科学影响外，该项目还将为下一代顶尖科学家提供研究机会，并为国家的科学、技术、工程和数学（STEM）劳动力做出贡献。Fayer集团将采用超快红外非线性光谱方法，特别是二维红外（2D IR）、偏振选择性泵浦-探测（PSPP）和超快光外差检测的光学克尔效应（OHD-OKE）实验，以探测高浓度的盐和酸溶液。盐溶液通常被称为“盐中的水”。它们的水分子太少，无法完全溶解离子，例如，一个离子对对应四个水分子酸溶液也将具有非常高的浓度。在酸性溶液中，水合氢离子取代了盐溶液中的阳离子。虽然水合氢离子是阳离子，但它可以通过转移质子将其身份改变为水分子。盐和酸溶液由扩展的离子/水网络而不是水合离子组成。实验将作为离子浓度和温度的函数进行。此外，单原子和多原子离子之间的差异和它们的相对大小的影响将进行研究。上述方法是一套相互关联的工具，将用于检查同一系统的不同方面，使动力学，结构和散装属性之间的关系的基本理解。该奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

With support from the Chemical Structure, Dynamics, and Mechanisms-A (CSDM-A) program in the Division of Chemistry, Professor Michael Fayer of Stanford University is developing sophisticated ultrafast spectroscopies to study the dynamics and structure of solvated ions and protons. Salt and acid solutions are common in nature and important in technological applications. The challenge in directly investigating ions in water is that the ion/water dynamics occur on exceedingly short time scales, trillionths of a second, or a billion times faster than a camera shutter speed. Professor Fayer and his students will advance ultrafast infrared and visible spectroscopic methods and use them to study concentrated salt and acid solutions. Their discoveries will enhance basic knowledge of important ion/water systems and lead to better understanding of complex electrolytes, such as those being developed for use in batteries for energy storage. In addition to the direct scientific impact through the sharing of information and technologies with academia, government laboratories, and industry, the project will provide research opportunities for the next generation of top scientists and contribute to the Nation's science, technology, engineering, and mathematics (STEM) workforce.The Fayer group will employ ultrafast infrared nonlinear spectroscopic methods, particularly two-dimensional infrared (2D IR), polarization selective pump-probe (PSPP), and ultrafast optical heterodyne detected optical Kerr effect (OHD-OKE) experiments to probe highly concentrated salt and acid solutions. The salt solutions are frequently referred to as “Water in Salt”. They have far too few water molecules to fully solvate the ions, e.g., one ion pair for four water molecules. The acid solutions will also have very high concentrations. In the acid solutions, hydronium replaces the cation found in salt solutions. While hydronium is a cation, it can change its identity to a water molecule by transferring a proton. The salt and acid solutions are composed of extended ion/water networks rather than hydrated ions. The experiments will be conducted as a function of ion concentration and temperature. In addition, the differences between monatomic and polyatomic ions and the effects of their relative sizes will be investigated. The methods mentioned above are a set of interrelated tools that will be used to examine different aspects of the same systems, enabling a fundamental understanding of the relationships among dynamics, structure, and bulk properties.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.