Rod Wasylishen, PhD
NMR spectroscopy is one of the most important and versatile techniques for characterizing the structure and dynamics of molecules. Traditionally, high-resolution NMR studies have been confined to isotropic liquid samples because solids are thought to yield broad featureless NMR spectra. Over the past twenty years, several ingenious experimental techniques have been devised to eliminate the line-width problem. There are many advantages to using NMR to investigate solid materials and much of our research has involved developing and exploring applications of these techniques. We have been particularly interested in measuring the orientation dependence of the NMR chemical shifts, spin-spin coupling constants and quadrupolar coupling constants using a variety of techniques such as single-crystal NMR spectroscopy. In addition to experimentally measuring these fundamental NMR parameters, their interpretation in terms of electronic and molecular structure has been of considerable interest. Typically, our experimental data are complemented by state-of-the-art ab-initio molecular orbital calculations. The goal of this research is to obtain a better understanding of magnetic shielding, spin-spin coupling and electric field gradient tensors.
Other interests include development of new solid-state NMR techniques, e.g., pulse programs designed to enhance the NMR signal of the central transition of half-integer quadrupolar nuclei and techniques to allow the analysis of complex NMR spectra. We are also using the highest magnetic fields available (i.e., 21.14 T) for NMR studies to investigate important quadrupolar nuclei with small magnetic moments, such as 25Mg, 35/37Cl, 53Cr, 55Mn, 91Zr,95Mo and 115In. We tackle a diverse range of solid materials including paramagnetic systems, surfaces and porous materials. Using spin-exchange optical pumping techniques which utilize a 60 watt diode laser system, 129Xe nuclear spin population enhancements of approximately 104 are being realized. This makes 129Xe NMR an ideal technique for investigating the latter materials. With our 1H micro-imaging accessory, we have also investigated water management in operating fuel cells and are seeking to expand our imaging capabilities to other systems and nuclei.