PNNL

Abstract

This work was supported by the United States Department of Energy under grant number DE-FG07-99ER15012. ASL would like to acknowledge support from the National Institutes of Health (Federal grant EB002050) and the United States Department of Energy Office of Biological and Environmental Research Program (KP13-01-03-0-22142). GMB would like to thank Joseph Ford for assistance with the experimental aspects of the 900 MHz instrument. Part of the research described in this paper was performed in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. Support for the 11.74 T spectrometer at Penn State was provided by NSF grant CHE-9601572. Currently, the direct observation of strontium with solid-state nuclear magnetic resonance (NMR) is experimentally challenging. Strontium has a single NMR-active isotope (87Sr) that is quadrupolar (I = 9/2) with a low gyromagnetic ratio (? = -1.163x107 T-1 s-1) and a low natural abundance (~7%); factors which imply low sensitivity. Strontium nuclei located at lattice sites with moderate electric field gradients have been reported to possess large quadrupolar coupling constants, leading to broad resonances that further reduce sensitivity and limit the effectiveness of magic-angle spinning (MAS) experiments.[1, 2] In order to study strontium in samples where strontium nuclei are sparse, such as clays and zeolites, methods to enhance the sensitivity of 87Sr NMR must undergo further development.