High-Resolution Molecular Spectroscopy on Multiple Potential Energy Surfaces using Cavity-Ring-Down-Based Two-Photon Techniques

使用基于腔衰荡的双光子技术对多个势能表面进行高分辨率分子光谱分析

• 批准号: 1955310
• 负责人: Jinjun Liu
• 金额: $ 52.4万
• 依托单位: University of Louisville Research Foundation Inc
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1955310&HistoricalAwards=false
• 关键词: Resolution; Molecular; Spectroscopy; Multiple; Potential

In this project funded by the Chemical Structure, Dynamics, and Mechanisms A (CSDM-A) program of the Chemistry Division, Professor Jinjun Liu and his research team at the University of Louisville (UofL) are using sophisticated laser techniques to study the complex motions of nuclei and electrons in molecules, including electrons’ “orbiting” around the nuclei, the spin of electrons, and the vibrational and rotational motions of nuclei. In a molecule, these motions are “quantized”, meaning that they are not continuous but discrete. As a result, the molecule can be on separated “energy levels” with different energies and “quantum states”. Understanding the energy-level structure, and the distribution and transfer of energy between energy levels is essential to many disciplines of physical sciences. However, experimentally obtained data on the energy level structure of molecules are often extremely complicated and difficult to understand because different motions of electrons and nuclei coincide and are coupled to each other. Moreover, many quantum states are “dark”, i.e., they cannot be accessed from the lowest-energy state of the molecule using a single laser beam. These two factors often prohibit a comprehensive and quantitative understanding of the molecular energy level structure. The UofL team plans to overcome both obstacles by developing new spectroscopy techniques that use not one, but two laser beams to interrogate molecules. Using two laser beams provides the selectivity on energy levels that is necessary to simplify experimental data. It can also create “detours” to the dark states, given that intermediate quantum states are judiciously selected. In the experiment, the laser light is trapped between two mirrors that form an optical cavity, which significantly increases the time of interaction between the laser and molecules, and hence improves the detection sensitivity. The first molecules that the UofL team studies are nitrogen dioxide (NO2) and the nitrate radical (NO3). Both molecular species play important roles in the chemistry of the atmosphere. NO2 is one of the major pollutants of photochemical air pollution, while NO3 is the primary oxidant in the night-time troposphere. The UofL team is also collaborating with computational chemists to design their experiments and to interpret the expected experimental data.The project focuses on developing two high-resolution, high sensitivity spectroscopic techniques: double-resonance cavity ring-down (DR-CRD) and stimulated-emission pumping cavity ring-up (SEP-CRU). Both methods are based on the highly sensitive CRD technique. They have advantages associated with two-photon spectroscopy, including simplified spectra, sub-Doppler linewidth, and the capability of accessing molecular dark states, which cannot be accessed using single-photon spectroscopy techniques due to forbidding selection rules, small transition dipole moments, or unfavorable Franck-Condon factors. Quantitative information of vibronic (vibrational-electronic) coupling (e.g., the Jahn-Teller and pseudo-Jahn-Teller effects) and related intramolecular interactions (e.g., the spin-orbit interaction) are being investigated using these two new laser spectroscopic techniques. The first target molecules, NO2 and NO3, are two prototypical molecules for the study of vibronic interactions. They are interrogated with the DR-CRD and SEP-CRU techniques at room temperature and under jet-cooled conditions (T~1 K). With intermediate states for the two-step excitation predicted based on computational chemistry and spectroscopic models, the UofL team investigate the spin-rovibronic (spin-rotational-vibrational-electronic) energy level structure of the ground and low-lying excited electronic states of these two free radicals. Two previously developed spectroscopic models, one for vibronic analysis and the other for rotational analysis, have been combined and employed to simulate and fit the spin-rovibronic structure in experimentally obtained spectra, and to unravel the complex mechanism of vibronic interactions. In terms of scientific Broader Impacts, the experimental techniques and the theoretical model developed in this project are a uniquely effective tool for the study of spectroscopy and dynamics on multiple potential energy surfaces (PESs). The post-doctoral researcher and Ph.D. students engaged in this research project are gaining valuable experience in cutting-edge laser-spectroscopy technology, molecular physics, theoretical chemistry, and computer simulations of experimental data.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.

在这个由化学系化学结构、动力学和机制A（CSDM-A）项目资助的项目中，路易斯维尔大学（UofL）的刘进军教授和他的研究团队正在使用复杂的激光技术来研究分子中原子核和电子的复杂运动，包括电子围绕原子核的“轨道运动”、电子的自旋以及原子核的振动和旋转运动。在分子中，这些运动是“量子化的”，这意味着它们不是连续的，而是离散的。因此，分子可以处于具有不同能量和“量子态”的分离的“能级”上。了解能级结构，以及能级之间的能量分布和转移对物理科学的许多学科都是至关重要的。然而，实验获得的分子能级结构数据往往非常复杂，难以理解，因为电子和原子核的不同运动是一致的，并相互耦合。此外，许多量子态是“暗”的，即，它们不能使用单个激光束从分子的最低能量状态获得。这两个因素往往阻碍了对分子能级结构的全面和定量的理解。UofL团队计划通过开发新的光谱技术来克服这两个障碍，该技术使用不是一个，而是两个激光束来询问分子。使用两束激光提供了简化实验数据所必需的能级选择性。它也可以创造“绕道”到暗态，假定中间量子态是明智的选择。在实验中，激光被捕获在形成光学腔的两个反射镜之间，这显著增加了激光与分子之间的相互作用时间，从而提高了检测灵敏度。UofL团队研究的第一个分子是二氧化氮（NO2）和硝酸根（NO3）。这两种分子种类在大气化学中起着重要作用。NO2是大气光化学污染的主要污染物之一，而NO3是夜间对流层的主要氧化剂。UofL团队还与计算化学家合作，设计他们的实验并解释预期的实验数据。该项目专注于开发两种高分辨率，高灵敏度的光谱技术：双共振腔衰荡（DR-CRD）和受激发射泵浦腔衰荡（SEP-CRU）。这两种方法都是基于高灵敏度的CRD技术。它们具有与双光子光谱学相关的优点，包括简化的光谱、亚多普勒线宽和访问分子暗态的能力，由于禁止的选择规则、小的跃迁偶极矩或不利的弗兰克-康登因子，使用单光子光谱学技术无法访问分子暗态。电子振动（振动-电子）耦合的定量信息（例如，Jahn-Teller效应和伪Jahn-Teller效应）和相关的分子内相互作用（例如，自旋-轨道相互作用）正在使用这两种新的激光光谱技术进行研究。 第一个目标分子NO2和NO3是研究电子振动相互作用的两个原型分子。在室温和喷射冷却条件下（T~1 K），用DR-CRD和SEP-CRU技术对它们进行了询问。通过基于计算化学和光谱模型预测的两步激发的中间态，UofL团队研究了这两种自由基的基态和低位激发电子态的自旋-旋转-振动-电子（自旋-旋转-振动-电子）能级结构。两个先前开发的光谱模型，一个用于振动分析和其他的旋转分析，已被结合起来，并采用模拟和拟合的自旋-旋转振动结构在实验获得的光谱，并解开复杂的机制振动相互作用。在科学更广泛的影响方面，该项目中开发的实验技术和理论模型是研究多个势能面（PES）上的光谱学和动力学的独特有效工具。博士后研究员、博士。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

Calculated and Empirical Values of Vibronic Transition Dipole Moments of Reactive Chemical Intermediates for Determination of Concentrations

用于测定浓度的反应性化学中间体的电子振动偶极矩的计算值和经验值

• DOI: 10.1021/acs.jpca.3c01584
• 发表时间: 2023
• 期刊: The Journal of Physical Chemistry A
• 作者: Jones, Ian W.;Bersson, Jonathan S.;Liu, Jinjun;Sharma, Ketan;Vasilyev, Oleg A.;Miller, Terry A.;Stanton, John F.
• 通讯作者: Stanton, John F.

REVEALING LONG-RANGE SUBSTITUENT EFFECTS IN THE LASER-INDUCED FLUORESCENCE AND DISPERSED FLUORESCENCE SPECTRA OF JET-COOLED CHXF3−XCH2O (X = 1, 2, 3) RADICALS

揭示喷射冷却 CHXF3·XCH2O (X = 1, 2, 3) 自由基的激光诱导荧光和色散荧光光谱中的远距离取代基效应

• DOI: 10.15278/isms.2021.re08
• 发表时间: 2021
• 期刊: International Symposium on Molecular Spectroscopy (ISMS
• 作者: Liu, Jinjun;Tarczay, Gyorgy;Hegedus, Kristof;Telfah, Hamzeh;Reza, Md;Bazso, Gabor;Koncz, Benedek
• 通讯作者: Koncz, Benedek

Electronic spectroscopy of the A1̃2A′′/A2̃2A′−X̃2A′ transitions of jet-cooled calcium ethoxide radicals: Vibronic structure of alkaline earth monoalkoxide radicals of C s symmetry

喷射冷却乙醇钙自由基的 A1Ì2Aâ²â²/A2Ì2Aâ²âXÌ2Aâ² 跃迁的电子能谱：C s 对称性碱土金属单醇盐自由基的振动电子结构

• DOI: 10.1063/5.0056550
• 发表时间: 2021
• 期刊: The Journal of Chemical Physics
• 作者: Paul, Anam C.;Sharma, Ketan;Telfah, Hamzeh;Miller, Terry A.;Liu, Jinjun
• 通讯作者: Liu, Jinjun

Fine and hyperfine interactions of PbF studied by laser-induced fluorescence spectroscopy

激光诱导荧光光谱研究 PbF 的精细和超精细相互作用

• DOI: 10.1063/5.0099716
• 发表时间: 2022
• 期刊: Journal of Chemical Physics
• 影响因子: 4.4
• 作者: Chengcheng Zhu;Hailing Wang;Ben Chen;Yini Chen;Tao Yang;Jianping Yin;Jinjun Liu
• 通讯作者: Jinjun Liu

Laser-Induced Fluorescence Spectroscopy of Large Secondary Alkoxy Radicals: Part I. Spectral Overviews and Vibronic Analysis

大仲烷氧基自由基的激光诱导荧光光谱：第一部分：光谱概述和电子振动分析

• DOI: 10.1021/acs.jpca.0c10662
• 发表时间: 2021
• 期刊: The Journal of Physical Chemistry A
• 作者: Liu, Jinjun;Miller, Terry A.
• 通讯作者: Miller, Terry A.