Zero and ultra-low-field nuclear magnetic resonance

在化学测量和成像项目的支持下，加州大学伯克利分校的Alexander Pines和Dmitry Budker及其团队正在开发零磁场下的核磁共振（NMR），将其作为基础研究课题，并作为化学和材料科学的实用工具。这项工作将揭示磁共振中的新现象，并最终将核磁共振从对外部施加磁场的依赖中解放出来，从而导致便携式核磁共振化学分析和成像的新技术。在零磁场下，各向同性液体样品中的核自旋仅在电子介导的标量耦合（j -耦合）下演化。尽管在零场核磁共振中缺乏化学位移信息，但j -耦合对几何和电子结构的细微变化非常敏感，因此是精确化学信息的来源。因此，该研究计划的主要目标是演示零场核磁共振j光谱作为高精度化学指纹和分析技术。此外，为了从复杂光谱中分离化学信息，将重点开发用于零场多维光谱中特定异核和同核耦合解耦和重耦的多脉冲序列。这将涉及仪器的进步和对各向同性零场环境中平均哈密顿理论和相干转移的理论理解的发展，因为对称性与高场核磁共振中遇到的对称性根本不同。该研究计划还将研究零磁场下的核自旋单线态动力学，作为基础研究的主题，这将为生物医学应用的长寿命超极化态的实现提供见解。核磁共振是一种广泛应用于物理和生物科学的化学检测、表征和结构解析的技术。它也是磁共振成像（MRI）的基础。这项研究计划正在扩大核磁共振的能力，朝着一个新的方向发展；一种不需要昂贵且不可移动的超导磁体的方法。通过使用灵敏的原子磁强计来测量核磁共振信号，这项工作将使便携式和低成本的零场磁共振传感器具有潜在的应用范围，从环境测试到地球物理和空间研究，从医学到基础物理学。该项目为研究生和本科生提供多学科的培训，并为博士后研究人员提供指导，并促进与美国和国外科学家的研究合作。

With support from the Chemical Measurement and Imaging Program, Profs. Alexander Pines and Dmitry Budker and their groups at the University of California - Berkeley are developing nuclear magnetic resonance (NMR) in zero magnetic field as a subject of basic research and as a practical tool in chemistry and materials science. This work will uncover new phenomena in magnetic resonance and will eventually free NMR from its reliance upon externally imposed magnetic fields, leading to new technologies in portable NMR for chemical analysis and imaging. At zero magnetic field, nuclear spins in isotropic liquid samples evolve only under the electron mediated scalar couplings (J-couplings) between spins. Despite the absence of chemical shift information in zero-field NMR, the J-couplings are very sensitive to subtle changes in geometry and electronic structure and are thus a source of precise chemical information. As such, a primary goal of this research program is the demonstration of zero-field NMR J-spectroscopy as a technique for high-precision chemical fingerprinting and analysis. Furthermore, in order to disentangle chemical information from complex spectra, efforts will focus on the development of multi-pulse sequences for decoupling and recoupling specific heteronuclear and homonuclear couplings in zero-field multidimensional spectroscopy. This will involve advances in instrumentation and development of a theoretical understanding of average Hamiltonian theory and coherence transfer in the isotropic zero-field environment, as the symmetries are fundamentally different from those encountered in high-field NMR. The research program will also investigate nuclear-spin singlet state dynamics at zero magnetic field as a subject of basic research that will provide insight for the implementation of long-lived hyperpolarized states for biomedical applications.NMR is a widely used technique in the physical and biological sciences for chemical detection, characterization, and structure elucidation. It is also the basis of magnetic resonance imaging (MRI). This research program is expanding the capabilities of NMR by moving in a new direction; one that does not require costly and immobile superconducting magnets. By employing sensitive atomic magnetometers to measure NMR signals, this work will enable portable and low-cost zero-field magnetic resonance sensors with potential applications ranging from environmental testing to geophysical and space research to medicine to fundamental physics. This project is providing training to graduate and undergraduate students in multiple disciplines, as well as mentoring for postdoctoral researchers, and is catalyzing research collaborations with scientists from the USA and abroad.