Coherent Spectroscopy and Coherent Control of Molecules and Materials

分子和材料的相干光谱和相干控制

• 批准号: 1665383
• 负责人: Keith Nelson
• 金额: $ 62.75万
• 依托单位: Massachusetts Institute of Technology
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-07-15 至 2021-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1665383&HistoricalAwards=false
• 关键词: Coherent; Spectroscopy; Control; Molecules; Materials

In this project, funded by the Chemical Structure Dynamics and Mechanism-A (CSDM-A) program of the Chemistry Division, Professor Keith Nelson of the Massachusetts Institute of Technology is developing novel techniques that use short pulses of light in the terahertz (THz) frequency range of the spectrum. The terahertz range is just above the lower-frequency microwave (or GHz) range that is used in common devices like cellphones. Magnetic resonance measurements (similar to those in magnetic resonance imaging, or MRI) can reveal key information about molecular structure and bonding, but they have hardly ever been made at THz frequencies because of technological challenges with the sources of THz light. Professor Nelson overcomes these challenges using short THz pulses generated in a simple, tabletop-sized, experimental setup to make THz magnetic resonance measurements in about one minute. Measurements of molecular and biomolecular complexes with iron or similar elements are being conducted to understand molecular structures and how they change during chemical processes. The project has broader impacts in making facile and inexpensive THz measurement available to scientific communities in chemistry, biology, and materials science with applications spanning energy harvesting to chemical catalysis to biomedical measurement. In addition to providing training in cutting-edge spectroscopy techniques for graduate students and post-doctoral scientists, the Nelson research group also runs a unique outreach program (the Lambda Project) in which high school students come to MIT for hands-on experiments to learn about modern optics and modern materials.The project builds on recent demonstrations of THz electron paramagnetic resonance (EPR) in both the linear regime in which free-induction decays (FIDs) are measured and in the nonlinear regime in which 2-dimensional (2D) electron paramagnetic resonance (EPR) is carried out. THz EPR spectra of high-spin transition metal complexes with zero-field splittings that arise from spin-orbit coupling are measured. The splittings are highly sensitive to the ligands and their configuration around the central transition metal ion. The EPR measurement can be preceded by an optical ("pump") pulse that initiates photochemical changes, with associated changes in the spin states monitored on picosecond time scales. 2D THz EPR measurements, demonstrated on the collective spin states of magnetic materials, are being extended to multinuclear organometallic complexes in order to measure spin-spin interactions between the transition metal ions, revealing detailed information about the ground and excited-state electronic structures of the complexes. In addition to these measurements in which THz magnetic fields coherently drive electron spins, the combined THz electric and magnetic field components are being used to drive both electric and magnetic dipole moments of chiral molecules in experiments that seek new methods for enantiometric separation. Further impacts in chemistry and biology may be realized if improved enantiomeric separation can be achieved.

在这个项目中，由化学部化学结构动力学和机理-A (CSDM-A) 项目资助，麻省理工学院的 Keith Nelson 教授正在开发使用太赫兹 (THz) 短脉冲光的新技术频谱的频率范围。太赫兹范围略高于手机等常见设备中使用的低频微波（或 GHz）范围。磁共振测量（类似于磁共振成像或 MRI 中的测量）可以揭示有关分子结构和键合的关键信息，但由于太赫兹光源的技术挑战，它们几乎从未在太赫兹频率下进行过。尼尔森教授克服了这些挑战，利用在简单的桌面大小的实验装置中生成的短太赫兹脉冲，在大约一分钟内进行太赫兹磁共振测量。人们正在对含有铁或类似元素的分子和生物分子复合物进行测量，以了解分子结构以及它们在化学过程中如何变化。该项目在为化学、生物学和材料科学领域的科学界提供简便且廉价的太赫兹测量方面具有更广泛的影响，其应用涵盖能量收集、化学催化和生物医学测量。 除了为研究生和博士后科学家提供尖端光谱技术培训外，尼尔森研究小组还开展了一项独特的外展计划（Lambda 项目），让高中生来到麻省理工学院进行动手实验来学习关于现代光学和现代材料。该项目建立在最近的太赫兹电子顺磁共振（EPR）演示的基础上，在线性状态下测量自由感应衰变（FID），在非线性状态下测量二维(2D)进行电子顺磁共振(EPR)。测量了自旋轨道耦合产生的具有零场分裂的高自旋过渡金属配合物的太赫兹 EPR 光谱。分裂对配体及其围绕中心过渡金属离子的构型高度敏感。 EPR 测量之前可以有一个光学（“泵浦”）脉冲，该脉冲引发光化学变化，并在皮秒时间尺度上监测自旋状态的相关变化。二维太赫兹 EPR 测量在磁性材料的集体自旋态上得到证明，正在扩展到多核有机金属配合物，以测量过渡金属离子之间的自旋-自旋相互作用，揭示有关磁性材料的基态和激发态电子结构的详细信息复合物。除了太赫兹磁场相干驱动电子自旋的测量之外，在寻求对映体分离新方法的实验中，组合的太赫兹电场和磁场分量还被用来驱动手性分子的电偶极矩和磁偶极矩。 如果可以实现改进的对映体分离，则可能会实现对化学和生物学的进一步影响。

项目成果

Nonlinear rotational spectroscopy reveals many-body interactions in water molecules

非线性旋转光谱揭示水分子中的多体相互作用

• DOI: 10.1073/pnas.2020941118
• 发表时间: 2021
• 期刊: Proceedings of the National Academy of Sciences
• 作者: Zhang, Yaqing;Shi, Jiaojian;Li, Xian;Coy, Stephen L.;Field, Robert W.;Nelson, Keith A.
• 通讯作者: Nelson, Keith A.

THz-frequency magnon-phonon-polaritons in the collective strong-coupling regime

• DOI: 10.1063/1.5083849
• 发表时间: 2019-06-07
• 期刊: JOURNAL OF APPLIED PHYSICS
• 影响因子: 3.2
• 作者: Sivarajah, Prasahnt;Steinbacher, Andreas;Nelson, Keith A.
• 通讯作者: Nelson, Keith A.