MRI: Development of a broadband terahertz electron paramagnetic resonance spectrometer

MRI：宽带太赫兹电子顺磁共振波谱仪的研制

• 批准号: 1828570
• 负责人: Keith Nelson
• 金额: $ 52.85万
• 依托单位: Massachusetts Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-08-15 至 2022-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1828570&HistoricalAwards=false
• 关键词: MRI; Development; broadband; terahertz; electron

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.

该奖项得到了主要研究仪器、化学研究仪器以及化学测量和成像项目的支持。麻省理工学院的 Keith Nelson 教授和同事 Robert Griffin 开发了一种宽带太赫兹 (THz) 电子顺磁共振 (EPR) 光谱仪。太赫兹能量也称为亚毫米辐射、太赫兹波，其频率极高，位于电磁波谱中的红外辐射和微波辐射之间。新仪器能够测量线性响应 EPR 光谱和非线性 EPR 光谱，包括二维 (2D) 光谱。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（在低温下工作的磁铁）来提高灵敏度。测量是使用太赫兹场进行的，太赫兹场使用独特的基于波导的太赫兹信号生成和读出平台。一般来说，EPR 光谱仪可提供分子和固态材料的几何和电子结构的详细信息。它还用于获取有关自由​​基、短命、高活性物质的寿命的信息，这些物质参与有价值的化学转化以及可能的病理生长的启动。这些研究影响许多领域，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意义的化合物。该工具采用了受正在进行的研究启发的示例，是麻省理工学院本科生和研究生研究和教学的一个组成部分。它也被许多合作机构的研究人员使用，例如加州大学伯克利分校和加州大学戴维斯分校。这种新型光谱仪具有任何商用仪器尚不具备的功能。该 EPR 光谱仪支持使用分子磁体的稳态太赫兹 EPR 光谱、过渡金属光化学的时间分辨太赫兹 EPR 光谱（加州大学伯克利分校）以及金属蛋白的零场和高场太赫兹 EPR 光谱进行研究。它还用于测试析氧反应催化剂（加州大学戴维斯分校）的异金属氧化模型以及研究量子自旋液态。新的光谱仪对于评估提供一维伊辛链中分数自旋激发信息的化合物至关重要，其中伊辛代表了统计力学中使用的铁磁性数学模型，可以识别相变。该奖项反映了 NSF 的法定使命，并已被通过使用基金会的智力优点和更广泛的影响审查标准进行评估，认为值得支持。