th  - 1988 - 51st ENC Conference

204 RECENT PROGRESS IN HIGH RESOLUTION NMR OF SOLIDS. Charles
E. Bronnimann, Stephen L. Dec, James S. Frye, Bruce L.
Hawkins and Gary E. Maciel, Regional NMR Center, Colorado State
University, Fort Collins, CO 80523
Over the past several years this NSF-sponsored regional instrumentation facili-
ty (303-491-6455) has developed and applied a number of experimental strategies in
ongoing NMR studies of a variet~ of solids.loTe~niques used have included CP/MAS,
very high speed (> 20 KHz) MAS, =H CRAMPS, =~F-~C cross polarization, magic-angle
hopping and angle flipping; in each case the necessary instrumentation has been de-
signed and developed in the laboratory. Classes of materials that have been studied
include a variety of crystalline and amorphous organic and inorganic solids, poly-
mers and polymer blends, catalytically important surface systems, materials impor-
tant in separation science, organic goechemical solids, solid electrolytes, semi-
conductors and superconductors.
Current experimental thrusts in this laboratory include the improvement of 1H
CRAMPS characteristics, time-domain CRAMPS experiments, use of higher magnetic
fields (11.7 and 14.0 T) and higher MAS rates (> 23 kHz), development of new pulse
sequences, use of multiple-quantum techniques for examining hydrogen clustering,
improving pulse programming capabilities, and the integration and networking of
modern and more powerful computer capabilities with our spectrometers.
Selected examples of recent developments in these areas will be presented and
discussed.
205
HIGH-FIELD PULSED GRADIENTDIFFUSIONMEAS~S
Ronald L. Haner and Thomas Schleich
Department of Chemistry, University of California
Santa Cruz, CA 95064
Self-diffusion measurements obtained by the use of pulsed gradient spin echo
(PGSE) techniques are usually performed with modified spectrometers containing
resistive magnets at static fields of 2.35 Tesla or less. Few measurements have
been reported using spectrometers with superconducting magnets, and all have been
done with relatively weak gradient strengths. We have developed pulsed gradient
diffusion instrumentation for use in high field (7.05 Tesla) spectrometer systems,
employing gradient strengths that have been tested up to I00 gauss/cm.
The apparatus includes specially designed gradient probes and a simple,
stable current pulser. The gradient coil fringe field is minimized by using an
active screen, similar in design to that proposed by Mansfield and Chapman (J__~.
Phys. E: Sci. Instrum. t 19, 540, 1986).
Our PGSE spectrometer has been used to measure protein and solvent diffusion
in protein solutions and i__nn vitro intact cellular systems. Lysozyme
self-diffusion has been measured to an accuracy and precision of 5-10% in aqueous
solutions at concentrations as low as 0.5% w/w. Solvent (H20 and }[DO)
self-diffusion coefficients have been measured to an accuracy and precision of
less than 3%. Extensions to studies of restricted and anisotropic diffusion,
other nuclei, and spatially localized applications are anticipated.
The description of this high field PGSE spectrometer system, experimental
protocol, and some experimental results will be presented. (Supported by NIH
grant EY 04033.)
201