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

在这个由化学结构，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Stephen Drucker教授正在研究紫外线（UV）如何影响化学反应。 由光照射引起的化学反应称为光化学反应。 这些反应可能导致环境问题。 另一方面，它们在仔细控制的条件下进行时也是有益的。 例如，光化学反应可以用来制造有益于社会的新材料。 将来，关于光化学反应发生时所采取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过程中产生的分子结构，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。 Drucker教授的研究使用激光光谱学来测试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本科生获得激光，电子，计算化学和实验设计的经验。 这个研究项目有助于他们为研究生课程和基于STEM的职业做好准备。在这个项目中，学生记录了气相单环烯酮分子中单重态-三重态跃迁的振动分辨光谱。研究中的分子是2-环戊烯-1-酮（2CPO）、2-环己烯-1-酮（2CHO）和4 H-吡喃-4-酮（4PN）。目的是确定测试分子的最低三重激发态中振动模式的基频。该项目的重点是三重态振动的C=O/C=C拉伸区域的光谱。实验确定的基本原理，这些伸缩模式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量区域，靠近S 0-T1跃迁的原始带。在以前的工作中，研究小组在室温下使用腔衰荡（CRD）光谱来测量低频基本原理。然而，在较高频率的C=O伸缩区域，在室温下的S 0-T1 CRD带往往被淹没的振动热带属于S 0-S1过渡。为了消除这种干扰，本项目中的S 0-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。实验确定的激发态的基本频率进行比较，从各种国家的最先进的计算方法的预测。研究的广泛影响促进了大学生的学术和智力发展。这些教育活动包括科学培训，通过开发计算化学课程增强UW-Eau Claire的学术课程，以及扩大STEM中代表性不足的群体对当代物理化学研究的访问。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。

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.