Intermediate motions in organic solids as studied by solid-state NMR

The most important issue for studying molecular dynamic processes is to characterize both the motion amplitudes and time constants over a wide dynamic range, involving the application of several dynamic NMR methods. One possibility to investigate such processes are so-called Seperated-Local Field experiments, however, the usual applications of the SLF experiments are performed in the fast-motion regime, where they are only sensitive to the motion amplitudes. By slowing down the dynamic process by decreasing the temperature, one can reach the so-called intermediate-motion regime, at which the time constant of the dynamic process is similar to the inverse coupling constant of the anisotropic interaction. We will work out the theory as well as experimental results for DIPSHIFT experiments applied in the intermediate-motion regime. For the extraction of kinetic parameters, the comparison of the experiments with calculated data is necessary.