Ultrafast 2DIR Studies of Dynamics in Dense Gas and Supercritical Fluid Solutions

稠密气体和超临界流体溶液动力学的超快 2DIR 研究

• 批准号: 2102427
• 负责人: Lawrence Ziegler
• 金额: $ 54.38万
• 依托单位: Trustees of Boston University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-08-01 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2102427&HistoricalAwards=false
• 关键词: Ultrafast; 2DIR; Studies; Dynamics; Dense

With support from the Chemical Structure, Dynamics, and Mechanisms-A (CSDM-A) Program in the Division of Chemistry, Professor Lawrence Ziegler and his group at Boston University are investigating how molecules behave in supercritical fluids (SCFs). SCFs are a special state of matter found at high pressure and temperature, where the difference between liquid and gas vanishes. How well other molecules dissolve in a SCF is readily tunable, because the fluid properties are sensitively dependent on temperature and pressure. The tunable properties of SCFs are already being used for a wide range of applications in the energy, food, and pharmaceutical industries. However, SCFs have the potential for even greater impact as an inexpensive, efficient, and environmentally clean alternative to organic solvents that have negative environmental and human health consequences. The Ziegler group is conducting experiments with very short-duration pulses of infrared laser light to determine how molecules dissolve and lose their energy in SCFs. These measurements reveal whether dissolved molecules are found in spatial regions that are more liquid- or gas-like, how long they stay in such regions, and what molecular properties determine these behaviors. The research group also uses computational methods to gain additional insight into the behavior of molecules in a SCF by comparison with the experiments. This research challenges fundamental concepts that students in beginning general chemistry classes are taught about SCFs. Aside from the research activities, the research team mentors undergraduate and high school participants in Boston University’s ongoing NSF Research Experience for Undergraduates (REU) and Research in Science and Engineering (RISE) programs, respectively, in order to expand the impact of these studies and contribute to the development of the next generation of molecular scientists. The goal of this project is to exploit ultrafast two-dimensional infrared spectroscopy (2DIR) to gain a more detailed understanding of the local solvation environments in dense gases and supercritical fluids. While previous ultrafast 2DIR studies have been carried out for vibrating molecules in condensed-phase solutions, this project exploits the special characteristics of 2DIR spectra of dense gases and supercritical fluids to learn about rotational and vibrational relaxation in dense fluids, special solvation effects in the supercritical fluid phase, and the evolution of liquid phase character as a function of fluid density. The echo-like properties of 2DIR allow rotational energy relaxation rates of solutes to be precisely determined in high density and supercritical fluid solutions, where the rotational structure is completely unresolvable in the linear IR spectra. Unlike pump-probe spectroscopy, 2DIR directly reports on solvent fluctuations, and thus offers a window on the role of fluctuations in the local solvation dynamics of molecules in the region of the critical point. Additionally, 2DIR spectra distinguish free rotor and liquid-like character at a given state point, thus providing new molecular-level descriptions of these high-pressure and high-temperature regions of phase space that can be compared with previously established descriptions of inhomogeneities in the supercritical region. The different rates of vibrational and rotational energy relaxation are contrasted by these studies, which highlights the quantum bottlenecks for restoring equilibrium in dense, highly excited molecular systems. Finally, the researchers are working with the Boston University Instructional Production Services Team to develop a series of video lectures to accompany each chapter of a book on the principles of linear and nonlinear spectroscopy that is intended for beginning graduate and upper-division undergraduate students, as well as the greater science, technology, engineering, and mathematics (STEM) community.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.

在化学结构，动力学和机制-A（CSDM-A）计划的支持下，劳伦斯·齐格勒教授及其波士顿大学的小组正在研究分子在超临界流体（SCF）中的表现。 SCF是在高压和温度下发现的特殊物质，其中液体和气体之间的差异消失。其他分子溶解在SCF中的程度很容易调节，因为流体特性敏感地取决于温度和压力。 SCF的可调节性能已经用于能源，食品和制药行业的广泛应用。但是，SCF可能会成为具有负面环境和人类健康后果的有机解决方案的廉价，高效和环境清洁的替代方案，从而有可能产生更大的影响。 Ziegler组正在使用非常短的红外激光脉冲进行实验，以确定分子如何在SCF中溶解并损失其能量。这些测量值揭示了在更液体或气体的空间区域中是否发现了溶解的分子，它们在此类区域停留了多长时间以及哪些分子特性决定了这些行为。研究小组还使用计算方法与实验相比，可以进一步了解SCF中分子的行为。这项研究对基本概念提出了挑战，即在开始通用化学课程的学生中教授有关SCF的研究。除研究活动外，研究团队的指导者是波士顿大学正在进行的NSF研究经验（REU）（REU）和科学与工程学（RISE）计划（RIES）计划的本科生和高中参与者，以扩大这些研究的影响并为下一代分子科学家的发展做出贡献。该项目的目的是利用超快二维红外光谱（2DIR），以对密集气体和超临界流体中局部溶液环境有更详细的了解。虽然已经进行了以前的Ultrafast 2DIR研究，以用于凝结相溶液中的振动分子，但该项目利用了密集气体和超临界流体的2Dir光谱的特殊特征，以了解在密集流体中的旋转和振动式放松，在超级策略液相中的特殊溶液在液体相位的液体相位和液体液体的效果。 2DIR的回声样性能使溶液的旋转能弛豫速率可以精确确定在高密度和超临界流体溶液中，其中旋转结构在线性IR光谱中完全无法解决。与泵探针光谱法不同，2DIR直接报道了溶剂波动，因此为波动在临界点区域的分子局部溶液动力学中的作用提供了一个窗口。此外，2DIR光谱在给定状态点区分了自由转子和液体样特征，从而提供了这些高压和高温相位空间的新分子级描述，这些区域可以与以前确定的对超临界区域的不均匀性的描述进行比较。这些研究将振动和旋转能量松弛的不同速率对比了，这突出了量子瓶颈，以恢复在密集的，令人兴奋的分子系统中。最后，研究人员正在与波士顿大学教学生产服务团队合作，开发一系列视频演讲，以参与一本关于线性和非线性光谱原理的书的每一章，该章节旨在开始毕业生和上级本科生的本科生，以及较大的科学，技术，工程学和数学奖学金（STEM）奖学金。基金会的智力优点和更广泛的影响评论标准。

项目成果

Ultrafast 2DIR comparison of rotational energy transfer, isolated binary collision breakdown, and near critical fluctuations in Xe and SF 6 solutions

Xe 和 SF 6 溶液中旋转能量传递、孤立二元碰撞击穿以及近临界波动的超快 2DIR 比较

• DOI: 10.1063/5.0118395
• 发表时间: 2022
• 期刊: The Journal of Chemical Physics
• 作者: Rotondaro, Matthew C.;Jain, Arkash;Erramilli, Shyamsunder;Ziegler, Lawrence D.
• 通讯作者: Ziegler, Lawrence D.