Coherent Control of Spin Dynamics to Improve Spectral and Spatial Resolution in NMR

University Of Miami, Coral Gables FL

Investigators

Abstract

With support from the Chemical Measurement and Imaging Program, Professor Jamie Walls and his group at the University of Miami are working to develop cost-effective methods to improve the resolution of nuclear magnetic resonance (NMR) spectrometry, a powerful and versatile tool widely used in academic, clinical, and industrial research. If successful, this work will enable improved contrast in magnetic resonance imaging (MRI), a noninvasive tool widely used for clinical diagnostics and other imaging applications. This in turn could improve characterization and diagnosis of cancer and other difficult-to-detect ailments in the human body, as well as improving spatial resolution of images of solids such as bone. Dr. Walls is also developing software that will enable others to emulate and expand on his methods. Undergraduate and graduate students working on this research receive training in both theoretical and experimental aspects of NMR. In spectroscopy, two resonances can be resolved if their frequency difference, ????, is larger than the linewidths of the individual resonances. In NMR, improving spectral resolution is one of the most important challenges for extending the range of problems NMR can address. The PI's group recently discovered that unexpected improvements in spectral resolution could be achieved (1) by using low-power RF excitation in solid-state systems, (2) by using delayed-acquisition to highlight spectral differences due to Fourier dephasing, which is a result of the mathematical properties of the line shape and is independent of the underlying spin dynamics and/or complexity, or (3) by generating multispin-order in the presence of partially correlated radiofrequency (RF) and magnetic field B0 inhomogeneities in liquid-state samples. Collectively, these results suggest an alternative and unexplored route towards improving spectral resolution in NMR that forms the basis of this research. Specifically, the Walls group is developing pulse sequences that exploit differences in Fourier dephasing in order to enhance sharp spectral features in a spectrum. The work entails both theoretical and experimental investigations into the nature of the multispin-order that can lead to optimal line narrowing in liquid-state NMR. It can provide alternative methods for coherently improving resolution in both solid- and liquid-state NMR applications. These improvements can enhance spectroscopic characterization of pharmaceuticals, complex sugars, and other biomolecular species in addition to improving spatial resolution in solid-state MRI. 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.