Spectroscopy and Molecular Aggregation in Helium Droplets

氦液滴中的光谱学和分子聚集

• 批准号: 2102318
• 负责人: Andrey Vilesov
• 金额: $ 53.95万
• 依托单位: University of Southern California
• 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: 2021-08-15 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2102318&HistoricalAwards=false
• 关键词: Spectroscopy; Molecular; Aggregation; Helium; Droplets

With support from the Chemical Structure Dynamics and Mechanisms (CSDM-A) program of the Chemistry Division, Professor Andrey Vilesov of the University of Southern California, will study the structure of molecular cations (molecules with an electron removed) using infrared lasers. Cations are important active participants in a multitude of chemical reactions. However, the molecular structure of many cations remains unknown because their high reactivity makes it difficult to prepare sufficient amounts for study. These experimental challenges are to be overcome by isolating the cations in tiny droplets of liquid helium at temperatures close to absolute zero (-460 F), at which the cations have clean spectra. This line of research is expected to provide insights into how the outcome of a chemical reaction in different settings from outer space to industry is influenced by the structure of the cationic intermediates in the reaction. This project also will examine how molecules rotate and combine at very low temperature. The students engaged in this research project will gain valuable experience in both modern physical chemical experimentation and in data analysis. This project is focused on the study of the structure and quantum solvation of carbocations at an ultra-low temperature of 0.4 K in helium droplets. The droplets are produced in a cryogenic nozzle beam expansion, doped with molecular precursors, such as methane, ethene, and others and ionized by electron impact. The resulting cations encapsulated within the droplets will be irradiated in pulsed fashion from a tunable infrared laser. The resonance absorption of the radiation leads to release of the cations from the droplets followed by detection by the quadrupole mass spectrometer. The resulting infrared spectra in the range of C-H stretches are compared with the results of quantum chemical calculations to determine the structure of the cations. Solvation of the cations and small molecules in superfluid 4He and normal fluid 3He droplets will be studied by observation of the rotational structure in the spectra. The structure of the molecular aggregates will be obtained from the analysis of the x-ray diffraction using a free electron laser. The broader impacts of this work include potential societal benefits from exploring the structure and solvation of molecular cations which act as important chemical intermediates in condensed and gas phases. This project will provide opportunities for training of undergraduate and graduate students in science, technology, engineering, and mathematics (STEM) through the development and execution of cutting-edge physical chemical experiments and the preparation of ensuing publications.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.

在化学系化学结构动力学和机制（CSDM-A）计划的支持下，南加州大学的Andrey Vilesov教授将使用红外激光研究分子阳离子（去除电子的分子）的结构。阳离子是许多化学反应中重要的活性参与者。然而，许多阳离子的分子结构仍然未知，因为它们的高反应性使得难以制备足够的量用于研究。 这些实验挑战将通过在接近绝对零度（-460 F）的温度下将阳离子分离在液氦的微小液滴中来克服，在绝对零度下阳离子具有清晰的光谱。这一系列的研究有望深入了解从外层空间到工业的不同环境中化学反应的结果如何受到反应中阳离子中间体结构的影响。该项目还将研究分子如何在非常低的温度下旋转和联合收割机。参与该研究项目的学生将获得在现代物理化学实验和数据分析方面的宝贵经验。本项目主要研究0.4K超低温氦液滴中碳正离子的结构和量子溶剂化。液滴是在低温喷嘴束膨胀中产生的，掺杂有分子前体，如甲烷、乙烯等，并通过电子撞击电离。所得到的阳离子封装在液滴内，将被可调谐红外激光器以脉冲方式照射。辐射的共振吸收导致阳离子从液滴中释放，随后由四极质谱仪检测。在C-H伸缩范围内的红外光谱与量子化学计算的结果进行比较，以确定阳离子的结构。通过观察光谱中的转动结构，研究了超流4 He和正常流体3 He液滴中阳离子和小分子的溶剂化。分子聚集体的结构将通过使用自由电子激光的X射线衍射分析获得。这项工作的更广泛的影响包括探索分子阳离子的结构和溶剂化的潜在社会效益，这些分子阳离子在凝聚相和气相中作为重要的化学中间体。该项目将通过开发和执行前沿物理化学实验以及准备随后的出版物，为本科生和研究生提供科学、技术、工程和数学（STEM）培训的机会。该奖项反映了NSF的法定使命，并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，被认为值得支持。

项目成果

Infrared spectroscopy of ions and ionic clusters upon ionization of ethane in helium droplets

氦液滴中乙烷电离后的离子和离子簇的红外光谱

• DOI: 10.1063/5.0091819
• 发表时间: 2022
• 期刊: The Journal of Chemical Physics
• 作者: Erukala, Swetha;Feinberg, Alexandra J.;Moon, Cheol Joo;Choi, Myong Yong;Vilesov, Andrey F.
• 通讯作者: Vilesov, Andrey F.

Sizes of pure and doped helium droplets from single shot x-ray imaging

单次 X 射线成像的纯氦液滴和掺杂氦液滴的尺寸

• DOI: 10.1063/5.0080342
• 发表时间: 2022
• 期刊: The Journal of Chemical Physics
• 作者: Tanyag, Rico Mayro P.;Bacellar, Camila;Pang, Weiwu;Bernando, Charles;Gomez, Luis F.;Jones, Curtis F.;Ferguson, Ken R.;Kwok, Justin;Anielski, Denis;Belkacem, Ali
• 通讯作者: Belkacem, Ali