th  - 1988 - 51st ENC Conference

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I UNTRUNCATIO~I OF DIPOLE-DIPOLE COUPLINGS IN SOLIDS, OR ZERO FIELD
MON 9:0S I NMR ENTIRELY IN HIGH FIELD. Robert Tycko, AT&T Bell Laboratories,
Murray Hill, Nj, 07974.
N::R spectra of powdered or noncrystalline solids in high field commonly exhibit broad
lines that arise from the dependence of the nuclear magnetic dipole-dipole couplings
on molecular orientation. New experiments will be described in which that orientation
dependence is removed by the combination of rapid sample rotation with a synchronized
rf pulse sequence.• The sample rotation and pulse sequence have the effect of con-
verting the usual truncated dipole-dipole couplings into an untruncated form. The
result is N,~IR spectra with sharp lines and splittings that depend only on inter-
nuclear distances, i.e. spectra with a "zero field" appearance that are obtained
entirely in high field. Such spectra provide a means of studying molecular conforma-
tions in solids, without requiring single crystals. The theory behind untruncation
experiments will be presented along with experimental spectra of simple organic
solids.
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