High-Field Solid-State Dynamic Nuclear Polarization with Paramagnetic Systems Beyond Simple Spin 1/2

在化学系化学测量与成像项目的支持下，西北大学韩松义教授正致力于提高我们对固态动态核极化(DNP)的理解，这是提高核磁共振(NMR)灵敏度的重要手段，从而将其扩展到更广泛的化学体系。核磁共振是一种广泛使用的工具，用于表征化学体系的组成和动力学。例如，它是磁共振成像(MRI)的技术基础，磁共振成像是一种重要的医疗诊断工具。韩博士和她的团队正在设计新的探针和新的实验方案，以大幅提高对含有物种的样品和目前无法进行核磁共振分析的性质的核磁共振分析的分辨率和灵敏度。该研究通过提供技术和硬件开发的实践经验，为研究生提供跨学科的培训机会。教育影响通过一个结构化的本科生研究项目Hand-on-Spin(HSPIN)得到加强，该项目让本科生参与乐器开发。韩博士的研究重点是开发自旋操纵的创新方法和新的仪器能力，目标是提高对高场固态动态核极化(DNP)的理解和更广泛的适用范围。具体地说，她的团队正在使用一种新的增感方案来揭示来自高自旋系统的DNP，否则DNP是看不见的。在这些研究过程中，他们澄清了绝缘固体中Overhauser效应(OE)背后的机制，揭示了魔角旋转(MAS)下DNP中电子自旋交换(J)和偶极耦合(D)之间的竞争，并提高了对超精细DNP光谱测量过渡金属-核自旋距离的潜力和范围的理解。这些研究正在揭示新的数字核子处理器机制和新的实验方法，以将数字核子粒子扩展到S=1/2以外的自旋系统。这些目标是通过开发创新的仪器能力来实现的，这些能力包括同时进行电子(E)和核(N)自旋共振激发和检测；任意波形产生(AWG)脉冲整形以实现相干和/或自旋动力学辅助的e-n极化转移；以及在静态和MAS条件下的双频泵浦-探测器2D电子双共振(Eldor)。该奖项反映了美国国家科学基金会的法定使命，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 Chemical Measurement and Imaging Program in the Division of Chemistry, Professor Song-I Han at the Northwestern University is working to improve our understanding of solid-state Dynamic Nuclear Polarization (DNP), an important means of boosting the sensitivity of Nuclear Magnetic Resonance (NMR), thereby expanding its reach to a wider scope of chemical systems. NMR is a widely used tool for characterizing the composition and dynamics of chemical systems. It is, for example, the technical basis of Magnetic Resonance Imaging (MRI), an important medical diagnostic tool. Dr. Han and her group are devising new probes and new experimental protocols to substantially improve the resolution and sensitivity of NMR analysis of samples containing species and of properties currently not amenable to NMR analysis. The research offers interdisciplinary training opportunities to graduate students by providing hands-on experience in technology and hardware development. The educational impact is enhanced through a structured undergraduate research program, Hands-On-Spin (hSPIN), engaging undergraduate students in instrument development. Dr. Han's research focusses on development of innovative methods for spin manipulations and novel instrumental capabilities, targeting improved understanding and a wider scope of applicability for high-field solid-state Dynamic Nuclear Polarization (DNP). Specifically, her group is using a novel sensitizer scheme to reveal DNP from high-spin systems that would otherwise be invisible to DNP. In the course of these studies, they are clarifying the mechanism behind the Overhauser effect (OE) in insulating solids, unraveling the competition between electron spin exchange (J) and dipolar couplings (D) in DNP under Magic Angle Spinning (MAS), and improving understanding of the potential and range of hyperfine DNP spectroscopy to measure transition metal – nuclear spin distances. The studies are uncovering new DNP mechanisms and novel experimental approaches to extend DNP to spin systems beyond S=1/2. These aims are enabled by developing innovative instrumental capabilities for concurrent electron (e) and nuclear (n) spin resonance excitation and detection; arbitrary waveform generated (AWG) pulse shaping to achieve coherent and/or spin dynamics-assisted e-n polarization transfer; and two-frequency pump-probe 2D Electron DOuble Resonance (ELDOR), under static and MAS conditions.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.