MRI: Development of a broadband terahertz electron paramagnetic resonance spectrometer

该奖项由主要研究仪器，化学研究仪器和化学测量和成像计划支持。麻省理工学院的基思纳尔逊教授和同事罗伯特格里芬开发了一种宽带太赫兹（THz）电子顺磁共振（EPR）光谱仪。太赫兹能量也被称为亚毫米波辐射，太赫兹波，其具有极高的频率，在电磁波谱中福尔斯红外辐射和微波辐射之间。新仪器能够测量线性响应EPR谱和非线性EPR谱，包括二维（2D）谱。它使用放大的飞秒（十亿分之一秒的百万分之一）激光系统和9.4特斯拉低温磁体（一种在低温下工作的磁体）来提高灵敏度。测量是使用THz场进行的，THz场使用独特的基于波导的THz信号生成和读出平台。一般来说，EPR光谱仪可以提供有关分子和固态材料的几何和电子结构的详细信息。它还用于获得有关自由基寿命的信息，这些自由基是参与有价值的化学转化以及可能的病理性生长起始的短寿命、高反应性物种。这些研究影响了许多领域，从无机和有机分子的合成到新型固态材料的开发，再到具有磁性和生物学意义的化合物。从正在进行的研究中得到启发的例子，这个工具是麻省理工学院本科和研究生阶段研究和教学的一个组成部分。许多合作机构的研究人员也在使用它，如加州大学伯克利分校和加州大学戴维斯分校。该EPR光谱仪支持使用分子磁体的稳态THz EPR光谱和过渡金属光化学的时间分辨THz EPR光谱（UC Berkeley）以及金属蛋白质的零场和高场THz EPR的研究。它还用于测试析氧反应催化剂（加州大学戴维斯分校）的异金属氧化物模型和研究量子自旋液态。新的光谱仪是必不可少的评估化合物，提供信息的分数自旋激发在一个一维伊辛链，其中伊辛代表的数学模型的铁磁性用于统计力学，允许识别相变。这个奖项反映了NSF的法定使命，并已被认为是值得支持的评估使用基金会的智力价值和更广泛的影响审查标准。

This award is supported by the Major Research Instrumentation, the Chemistry Research Instrumentation and the Chemical Measurements and Imaging programs. Professor Keith Nelson from MIT and colleague Robert Griffin have developed a broadband terahertz (THz) electron paramagnetic resonance (EPR) spectrometer. The terahertz energy is also known as submillimeter radiation, terahertz waves, which have an extremely high frequency that falls in between infrared radiation and microwave radiation in the electromagnetic spectrum. The new instrument is capable of measuring both linear-response EPR spectra and nonlinear EPR spectra including two-dimensional (2D) spectra. It uses an amplified femtosecond (one millionth of one billionth of a second) laser system and a 9.4 Tesla cryomagnet (a magnet that operates a low temperatures) to increase sensitivity. The measurements are conducted using THz fields that use a unique waveguide-based THz signal generation and readout platform. In general, an EPR spectrometer yields detailed information on the geometric and electronic structure of molecular and solid-state materials. It is also used to obtain information about the lifetimes of free radicals, short-lived, highly reactive species involved in valuable chemical transformations as well as the initiation of possible pathological growth. These studies impact many areas, from the synthesis of inorganic and organic molecules to the development of new solid-state materials to compounds of magnetic and biological interest. Employing examples inspired from ongoing research, this instrument is an integral part of research and teaching at the undergraduate and graduate levels at MIT. It is also used by researchers at many collaborating institutions such as the University of California at Berkeley and the University of California at Davis.The new spectrometer has capabilities not yet available in any commercially available instrument. This EPR spectrometer supports research using steady-state THz EPR spectroscopy of molecular magnets and time-resolved THz EPR spectroscopy of transition metal photochemistry (UC Berkeley) and zero-field and high-field THz EPR of metalloproteins. It is also used to test heterometallic oxido models for oxygen-evolution reaction catalysts (UC Davis) and for studying quantum spin liquid state. The new spectrometer is essential to evaluate compounds that provide information on fractional spin excitations in a 1D Ising chain, where Ising represents a mathematical model of ferromagnetism used in statistical mechanics that allows the identification of phase transitions.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.