Decoding the Infrared Spectra of High Frequency Molecular Vibrations

分子可以通过它们的振动方式来检测和识别。 它们的振动通常发生在对应于红外光的频率。因此，通过观察分子如何吸收不同波长的红外光（实验室技术称为振动光谱学），我们可以了解它们的结构和性质。 然而，当分子变大时（换句话说，“多原子”，意味着许多原子），或者如果一个小分子被其他分子包围（例如，溶解在水中的酒精分子），它们的振动变得非常复杂，难以解释。在这个项目中，由化学部的化学结构，动力学和机制A资助，威斯康星大学麦迪逊分校的Edwin Sibert教授正在扩展当前的理论模型，以提高我们从多原子分子和溶解在液体中的分子的振动中提取结构信息的能力。这项研究有望提高我们解释分子结构及其与环境中其他分子相互作用的详细图片的能力。 在这项研究中开发的模型也对理解复杂的生物化学过程以及用于各种应用（包括药物和燃料）的分子的实际设计具有影响。 最后，Sibert研究小组还在为UW麦迪逊大学的本科化学课程开发电子学习资源。 Silbert教授参与为学生设计电子资源。这些资源从帮助学生理解在溶剂化现象中起作用的力量延伸到教育他们化学对我们社会的重大贡献。CH，NH和OH拉伸区域的液相红外光谱通常缺乏询问分子激发后原子核运动如何演变所需的光谱分辨率。在冷集群中采样的类似分子运动由类似的力控制，然而，由于有限的集群大小和寒冷的温度，这些高频振动的实验光谱具有足够窄的线形，光谱特征被揭示。该项目的目的是提供解释这些特征所需的理论工具，以揭示潜在的动力学并提取结构和环境信息。这些集群的有限大小也允许严格的测试的理论模型。该测试包括量化用于确定潜在力场的技术的质量。设计药物和预测燃烧反应的结果取决于化学家确定此类力场的能力，以便计算各种化学物质的相对稳定性并了解环境如何影响这些稳定性。该项目的广泛影响包括生成开源计算机软件，使科学家能够测量和理解这些稳定性，并为该研究领域的学生提供培训基地。该奖项反映了NSF的法定使命，并被认为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来支持。

Molecules can be detected and identified by how they vibrate. Their vibrations typically occur at frequencies corresponding to infrared light. Thus, by observing how molecules absorb different wavelengths of infrared light (the laboratory technique is called vibrational spectroscopy), we can tell something about their structure and properties. However, as molecules become large (in other words “polyatomic”, meaning many atoms), or if a small molecule is surrounded by other molecules (for example, an alcohol molecule dissolved in water), their vibrations become very complicated and difficult to interpret. In this project, funded by the Chemical Structure, Dynamics and Mechanisms A of the Chemistry Division, Professor Edwin Sibert of the University of Wisconsin-Madison is extending current theoretical models in order to enhance our ability to extract structural information from the vibrations of polyatomic molecules and molecules dissolved in liquids. This research is expected to enhance our ability to interpret get a detailed picture of a molecule’s structure and its interaction with other molecules in its environment. The models developed in this research also have implications for understanding complex biochemical processes as well as the practical design of molecules for a variety of applications, including pharmaceuticals and fuels. Finally, the Sibert research group is also developing electronic learning resources for the undergraduate chemistry program at UW Madison. Professor Silbert is involved in the design of electronic resources for students. These resources extend from helping students understand the forces at play in solvation phenomena to educating them about the significant contributions of chemistry to our society.Liquid phase infrared spectra of the CH, NH and OH stretch regions often lack the spectral resolution required to interrogate how the motions of nuclei evolve upon molecular excitation. The analogous molecular motions sampled in cold clusters are governed by similar forces, yet, due to the limited cluster size and cold temperatures, the experimental spectra of these high frequency vibrations have sufficiently narrow line shapes that spectral features are revealed. The aim of this project is to provide the theoretical tools that are required for interpreting these features in order to both reveal the underlying dynamics and extract structural and environmental information. The limited size of these clusters also allows for the rigorous testing of the theoretical models. This testing includes quantifying the quality of the techniques used to determine the underlying force fields. Designing drugs and predicting outcomes of combustion reactions depend on chemists’ ability to determine such force fields in order to calculate the relative stabilities of various chemical species and understand how environment affects those stabilities. The broader impact of this project includes generating open source computer software to enable scientists to measure and understand these stabilities as well as to provide a training ground for students in this research area.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.