- K. Saalwächter, I. Fischbach.
The Application of MAS Recoupling Methods in the
Intermediate Motional Regime.
J. Magn. Reson. 157, 17-30 (2002).
We present investigations concerning the effect of molecular motions on the
experimental timescale upon the recoupling of anisotropic interactions under
magic-angle spinning conditions. An approach for the efficient simulation of
spin dynamics occurring during complex pulse sequences, based on a
linearization of the general solution of the stochastic Liouville-von-Neumann
equation, was developed. Using 13C CSA
recoupling of the methyl carbon in dimethylsulfon as a sample interaction, we
observed a characteristic signal decay under recoupling upon entering the
intermediate motional regime, which can be well described by an apparent
transverse relaxation time, T2rcpl. This quantity does not depend
on the spinning frequency to a first approximation. Specific recoupling
experiments, namely the measurement of tensor parameters by spinning sideband
analysis, and the determination of rate constants with the CODEX experiment,
are discussed with respect to possibilities and limits of their application in
the intermediate motional regime.