RUI: Spectroscopic and Computational Studies of Cyclic Enone Molecules in Electronic Excited States

RUI：电子激发态环状烯酮分子的光谱和计算研究

• 批准号: 1955137
• 负责人: Stephen Drucker
• 金额: $ 33.46万
• 依托单位: University of Wisconsin-Eau Claire
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-07-15 至 2025-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1955137&HistoricalAwards=false
• 关键词: RUI; Spectroscopic; Computational; Studies; Cyclic

In this project funded by the Chemical Structure, Dynamics, and Mechanisms-A (CSDM-A), Professor Stephen Drucker of the University of Wisconsin-Eau Claire (UW-Eau Claire) is investigating how chemical reactions are affected by ultraviolet (UV) light. Chemical reactions started by exposure to light are called photochemical reactions. These reactions can contribute to environmental problems. On the other hand, they can also be beneficial when carried out under carefully controlled conditions. For instance, photochemical reactions can be used to make new materials that would benefit society. In the future, the most detailed information about the steps taken when photochemical reactions occur may come from computer modeling. Computational scientists can predict the structures of molecules produced during photochemical reactions, but the computational methods do not always yield accurate results and thus, they are still being improved. Professor Drucker’s research uses laser spectroscopy to test computational predictions on molecules that can take part in photochemical reactions. Undergraduate student researchers perform the experimental work. UW-Eau Claire undergraduates gain experience with lasers, electronics, computational chemistry and experiment design. This research project helps prepare them for graduate programs and STEM-based careers. In this project, students are recording vibronically resolved spectra of singlet-triplet transitions in gas-phase monocyclic enone molecules. Molecules under investigation are 2-cyclopenten-1-one (2CPO), 2-cyclohexen-1-one (2CHO), and 4H-pyran-4-one (4PN). The objective is to determine fundamental frequencies for vibrational modes in the lowest triplet excited states of the test molecules. The project focuses on triplet-state vibrations in the C=O/C=C stretch region of the spectra. Experimentally determined fundamentals for these stretching modes augment frequency information previously obtained for ring vibrational modes and carbonyl wagging modes. Those bands appear in the lower-energy region of each spectrum near the origin band of the S0-T1 transition. In previous work, the research group used cavity ringdown (CRD) spectroscopy at room temperature to measure the lower-frequency fundamentals. However, in the higher-frequency C=O stretch region, the S0-T1 CRD bands at room temperature tend to be submerged by vibronic hot bands belonging to the S0-S1 transition. To eliminate this interference, the S0-T1 spectra in this project are recorded under jet-cooled conditions, using two-color resonant enhanced two-photon ionization to detect the transitions. Experimentally determined excited-state fundamental frequencies are compared to predictions from a variety of state-of-the art computational methods. Broader impacts of the research promote academic and intellectual growth of undergraduate students. These educational activities include scientific training, enhancement of the academic curriculum at UW-Eau Claire through the development of a computational chemistry course, and the expansion of access to contemporary physical chemistry research by groups underrepresented in STEM.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.

在这项由化学结构、动力学和机制-A(CSDM-A)资助的项目中，威斯康星大学欧克莱尔分校(UW-Eau Claire)的斯蒂芬·德鲁克教授正在研究紫外线(UV)如何影响化学反应。由光引起的化学反应称为光化学反应。这些反应可能会导致环境问题。另一方面，如果在严格控制的条件下进行，它们也可能是有益的。例如，光化学反应可以用来制造造福社会的新材料。未来，有关光化学反应发生时采取的步骤的最详细信息可能来自计算机建模。计算科学家可以预测光化学反应中产生的分子结构，但计算方法并不总是产生准确的结果，因此，它们仍在改进中。德鲁克教授的研究使用激光光谱学来测试对可以参与光化学反应的分子的计算预测。本科生研究人员进行实验工作。UW-Eau Claire大学的本科生获得激光、电子学、计算化学和实验设计方面的经验。这项研究项目帮助他们为研究生课程和STEM职业生涯做好准备。在这个项目中，学生们正在记录气相单环烯分子中单重态-三重态跃迁的振动分辨光谱。被研究的分子是2-环戊烯-1-酮(2CPO)、2-环己烯-1-酮(2CHO)和4H-吡喃-4-酮(4PN)。其目的是确定测试分子最低三重态激发态的振动模式的基频。该项目主要研究光谱中C=O/C=C伸缩区的三重态振动。实验确定的这些伸缩模式的基本原理增加了以前获得的环振动模式和羰基摇摆模式的频率信息。这些带出现在每个光谱的较低能区，靠近S0-T1跃迁的原始带。在之前的工作中，该研究小组使用室温下的腔振荡器(CRD)光谱来测量较低频率的基波。然而，在较高频率的C=O伸缩区，室温下的S0-T1CRD带往往被S0-S1跃迁的振动热带淹没。为了消除这种干扰，本项目中的S0-T1光谱是在喷射冷却条件下记录的，使用双色共振增强双光子电离来检测跃迁。实验确定的激发态基频与各种最先进的计算方法的预测进行了比较。这项研究的更广泛影响促进了本科生的学业和智力成长。这些教育活动包括科学培训，通过开发计算化学课程来增强UW-Eau Claire的学术课程，以及扩大在STEM中代表性不足的团体获得当代物理化学研究的机会。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。