th  - 1987 - 51st ENC Conference

MFI7
A DOUBLE QUANTUM FILTER FOR ROTATING SOLIDS
AND SOME OBSERVATIONS ON LABELLING IN SOLIDS
William L. Earl" and Beat H. Meier t
Los Alamos National Laboratory
Mail Stop C345
Los Alamos, New Mexico 87545
For several years we have been investigating the use of 13C labelling in solid samples.
In our studies of multiple quantum coherence in solids, it occurred to us that it would
be interesting to use a solid state equivalent of the INADEQUATE experiment to trace
carbon connectivities. The difficulty with this experiment is that the dipole coupling,
used to generate the double quantum coherence, changes sign upon sample rotation. Last
year we demonstrated a pulse sequence which will generate and detect multiple quantum
coherences in the proton NMR of adamantane with MAS. The logical extension of that
experiment is a double quantum filter for 13C NMR of a rotating solid.
We will demonstrate the pulse sequence for such a double quantum filter. Since such a
filter selects for resonances with a homonuchar dipole coupling, we run into the problem
of commutation of the dipole coupling tensor with the chemical shift tensor, a problem
that has been addressed by Maricq and Waugh 1. We will show several 13C spectra which
demonstrate distortions in the NMR spectrum as a function of the extent of overlap of the
shift tensors of the dipolar coupled resonances.
1. M.M. Maricq and J.S. Waugh, J. Chem. Phys. 70, 3300 (1979).
t Present Address: Laboratorium ffr Physikalische Chemie, ETH-Zentrum, 8092 Zfirich,
Switzerland.