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 novel methods in chemical analysis based on nuclear magnetic resonance (NMR) spectroscopy of J-coupled systems at zero magnetic-field, using high sensitivity atomic magnetometers to monitor NMR signals. J-couplings are an important parameter in high-field NMR spectroscopy yielding important information about molecular bonding and nuclear spin topology, and are crucial for determination of molecular structure and function. The advantages of using atomic magnetometers to detect such couplings at zero magnetic-field are the high sensitivity of atomic magnetometers to low frequency signals, and the extremely high absolute magnetic field homogeneity, yielding very narrow magnetic resonance lines for high resolution. Major goals include optimization of sensitivity, development of multi-pulse sequences for decoupling and recoupling specific heteronuclear couplings in zero-field multidimensional spectroscopy, investigation of parahydrogen-induced polarization for enhancing signal, and the development of a rudimentary chemical fingerprinting library based on zero field J-spectra.
NMR is widely used to characterize materials across nearly all branches of the physical and biological sciences; it is the core of biomedical and other magnetic resonance imaging applications. This fundamental research is expanding the capabilities of NMR by developing and employing new approaches to creating and measuring the associated signals. By advancing the development of sensitive atomic magnetometers, the work will enable portable, low-field magnetic resonance imaging sensors with potential application in a wide variety of fields, ranging from geophysical and space research to medicine to tests of fundamental symmetries. It is providing training to both undergraduate and graduate students in multiple disciplines, as well as mentoring for several postdoctoral researchers.
Progress in nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance imaging (MRI) is conventionally associated with higher and higher magnetic fields. A typical high-field NMR instrument costson the order of $1 million, requires constant cryogenic maintenance, is immobile, and can’t be used on samples with metallic inclusions or implanted devices. This project has explored a somewhat unexpected recent trend toward using ultralow, submicrotesla fields—or even no external field at all. The new trend has been enabled by new techniques and technologies that have relaxed the requirement forlarge magnetic fields in each of the three main stages of an NMR experiment—polarization, encoding, and detection. Within the project, we used millimeter scale atomic sensors to detect NMR for chemical spectroscopy; scalar couplings for encoding; and various techniques for polarizing the sample, including parahydrogen induced polarization, whereby a full NMR experiment has been realized that did not rely on any magnets. The power of the technique for chemical analysis has been demonstrated through investigating a series of aromatic compounds. The project has resulted in publications in Physics Today, Nature Physics, JACS, Phys. Rev. Letters, and has served to train several graduate and undergraduate students and to catalyze research collaborations with scientists from Germany, Poland, and Japan.
