Advances in Zero-Field Nuclear Magnetic Resonance Spectroscopy (original) (raw)

In the course of the last century, Nuclear magnetic resonance (NMR) has become a powerful and ubiquitous analytical tool for the determination of molecular identity, structure, and function. Traditionally, the great analytical power of NMR comes at the cost of mobility and large expenses for cryogenic cooling. This thesis presents how zero-field NMR detected with an atomic magnetometer is emerging as a new, potentially portable and cost-effective modality of NMR with the ability of providing information-rich and highresolution spectra. A detailed description of the zero-field NMR spectrometer and its operation is provided. The thesis details how the acquired zero-field NMR spectra result from the electron mediated scalar interaction (J-coupling) of nuclear spins in an analyte. Simple rules of addition of angular momenta are introduced for the prediction of the observed spectral lines overcoming the need for numerical simulations and enabling unambiguous assignment of peaks to different molecules. Additional information can be obtained in the near zero field regime, where the Zeeman interaction can be treated as a perturbation to the J-coupling. The presence of small magnetic fields results in splitting of the zero-field NMR lines, imparting additional information to the pure zero-field spectra. In addition to the utilization of the atomic magnetometers for enhanced sensitivity, hyperpolarization schemes can be implemented. This thesis shows that chemically specific zero-field NMR spectra can be recorded using hydrogenative and non-hydrogenative parahydrogen induced polarization (PHIP, NH-PHIP), enabling high-resolution NMR. The increased sensitivity enables detection of compounds with 13 C or 15 N in natural abundance. Since PHIP and NH-PHIP operate in situ, and eliminate the need for a prepolarizing magnet, they broaden the analytical capabilities of zero-field NMR. Lastly, this thesis gives insight into the PHIP and NH-PHIP mechanism by developing an appropriate theoretical framework. i Dedication To my wife & to my son. ii Acknowledgments I am incredibly grateful for the fabulous opportunity to conduct all my graduate work in a great work environment and I want to thank each and everyone who has contributed, not only to the work, but also to the experience of grad school overall. It was a pleasure to interact with so many inspiring individuals. Any attempt of creating an exhaustive list of all the people that have contributed to the experience at Berkeley is prone fail. At the same time, I do want to express my gratitude to absolutely everybody that has made my experience into what it was and has thereby enabled this thesis. Foremost, I want to thank my adviser Alex Pines and my committee members Dima Budker and Dave Wemmer, who guided me through the Ph.D. program. My special thanks go to the people that were directly involved with my work and helped with all aspects of the work presented in this thesis: