th  - 1987 - 51st ENC Conference

MF77
NMR IMAGING OF SOLIDS
WITH A SURFACE COIL
J. B. Miller* and A. N. Garroway
Chemistry Division, Code 6120
Naval Research Laboratory
Washington, DC 20375-5000
A number of NMR techniques have already been
demonstrated to be useful for imaging solids. These
techniques are limited to small samples because
traditional coil geometries require large amounts of
power to generate the B 1 fields required for solid state
imaging. The use of surface coils can somewhat
circumvent this problem.
Several imaging strategies are possible using
surface coils, including rotating frame imaging and
"depth" sensitive excitation. Because of line broadening
in solids, resolution in the rotating frame experiment is
a problem. Multiple pulse line-narrowing has been used
for imaging solids; by virtue of its sensitivity to pulse
amplitude/duration it is a form of depth sensitive
excitation. Multiple pulse line-narrowing generally
requires large B 1 fields thus limiting its use to regions
very close to the surface coil.
We will present several examples of surface coil
imaging of solids employing multiple pulse line-
narrowing. We will discuss the dependence of line-
narrowing efficiency and depth sensitivity upon the
multiple pulse technique. We also introduce the "magic
angle nutation" sequence which is less sensitive to the
magnitude of the B 1 field than traditional line-narrowing
sequences.