Development of Ultrafast Cavity-Enhanced Two-Dimensional Spectroscopy for Coherent Control Experimental Design

在原子、分子和光学实验物理(AMO-E)、化学结构、动力学和机制-A(CSDM-A)和物理综合活动计划的支持下，佐治亚大学的Melanie Reber教授正在提高激光技术研究和控制分子的灵敏度。利用光选择性地控制键的断裂和控制化学反应的结果是一个由来已久的梦想。它可能会为合成分子甚至创造新分子提供新的途径。为了利用光进行受控合成，理想情况下，人们应该详细了解分子的电子、振动和旋转能量以及它们是如何耦合的。描述分子系统以设计控制序列的一个挑战是，如果分子具有复杂的动力学，而目前的计算化学或光谱方法不能很好地描述这些动力学。该项目将开发一种由光谱学驱动的方法来设计相干控制实验，特别是通过使用光学增强腔和频率梳激光器来提高二维光谱学的灵敏度和分辨率。二维光谱学提供了有关分子结构和动力学的信息，但目前只能用于凝聚相样品。在该项目的三年时间里，研究团队将开发对稀薄物种进行多维光谱的能力，例如，能够在没有溶剂影响的情况下研究小的、孤立的分子。从事这个高技术项目的学生将在电子学、光学、激光、真空技术、编程、数据分析、CAD设计和量子力学方面获得宝贵的跨学科培训。这一培训将为学生在工业和学术界的技术领域取得成功的职业生涯奠定基础。此外，PI将开始一个针对当地大学，包括几个HBCU的学生的年度研讨会，以了解化学和物理研究生院及其应用过程。研究团队将开发一种高分辨率和超快的二维光谱仪，用于表征分子中的振动和电子耦合，以详细的分子方法设计相干控制实验。该项目的主要目标是建立具有可见泵浦和可调谐可见光探头的腔增强型二维光谱仪，并采用双梳探测方案。他们将使用频率梳激光和技术，包括双梳检测，以提高灵敏度并实现高分辨率光谱检测。空腔增强将提高二维谱的灵敏度，从而首次用二维谱研究分子束中的稀疏物种。然后，该仪器将提供有关气相分子的结构和动力学的新数据，具有用于相干控制实验设计的超快时间分辨率和高精度频率分辨率的潜力。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。

With support from the programs in Atomic, Molecular and Optical Experimental Physics (AMO-E), Chemical Structure, Dynamics and Mechanisms-A (CSDM-A) and Integrative Activities in Physics, Prof. Melanie Reber at the University of Georgia is increasing the sensitivity of a laser technique for studying and controlling molecules. The idea of using light to selectively control the breaking of a bond and to control the outcome of a chemical reaction is a long-standing dream. It could potentially provide new avenues to synthesize molecules or even create new molecules. In order to use light for a controlled synthesis, ideally one would have detailed knowledge about the molecular electronic, vibrational, and rotational energy landscapes and how they are coupled. One challenge with describing the molecular system for designing control sequences is if the molecule has complicated dynamics that are not well described by current computational chemistry or spectroscopic methods. This project will develop a spectroscopy-driven approach to designing coherent control experiments, specifically improving the sensitivity and resolution of two-dimensional spectroscopy through the use of optical enhancement cavities and frequency comb lasers. Two-dimensional spectroscopy provides information about the structure and dynamics of molecules, but currently can only be used on condensed-phase samples. Over the three years of the project, the research team will develop the capability to perform multidimensional spectroscopy on dilute species, enabling studies of small, isolated molecules without the effects of solvent, for example. The students working on this highly-technical project will gain valuable interdisciplinary training in electronics, optics, lasers, vacuum technology, programming, data analysis, CAD design, and quantum mechanics. This training will set the students up for successful careers in technical fields in industry and academia. In addition, the PI will start a yearly workshop aimed at students from local colleges, including several HBCU’s, to learn about chemistry and physics graduate school and the application process.The research team will develop a high-resolution and ultrafast two-dimensional spectrometer for characterization of vibrational and electronic coupling in molecules for a detailed molecular approach to designing coherent control experiments. The main goal of the project is to build the cavity-enhanced two-dimensional spectrometer with a visible pump and tunable visible probe with a dual comb detection scheme. They will use frequency comb lasers and techniques, including dual-comb detection, to increase the sensitivity and enable high-resolution spectral detection. The cavity-enhancement will improve the sensitivity of two-dimensional spectroscopy, such that dilute species in molecular beams can be studied with two-dimensional spectroscopy for the first time. This instrument will then provide new data on the structure and dynamics of gas phase molecules with the potential for ultrafast time resolution and high-precision frequency resolution to be used for coherent control experimental design.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.