A simple analytical model to describe dynamic magic-angle spinning experiments

A simple analytical method based on the memory-function approach and the Anderson-Weiss theory is presented for studying in a uniform way the spin dynamics in several NMR experiments performed under the conditions of magic-angle spinning (MAS). A series of H-1 MAS spectra of adamantane serve as an example for a sample with homogeneous line broadening. A good agreement between experimental and calculated integral spinning sideband intensities for a spinning frequency ranging from 5 to 33 kHz is obtained using a sixth-order approximation of the theory. Moreover, this model, which is able to describe the NMR spectra in the presence of a rotationally diffusive isotropic and anisotropic Gaussian-Markoff process, allows the treatment of the combined effects of sample spinning and molecular motion. Finally, the application of MAS recoupling methods in the intermediate motional regime is examined by using the concept of refocusing pulses. it is shown that recoupling experiments such as rotational-echo double-resonance (REDOR) can still be applied in the presence of anisotropic molecular motion. (C) 2006 Wiley Periodicals, Inc.