Calculation of MAS spectra influenced by slow molecular tumbling.

A numeric algorithm is proposed that is suitable to calculate spectral lineshapes influenced by isotropic and anisotropic tumbling under sample spinning conditions. It is based on the stochastic Liouville equation and a rotational diffusion process described by a stationary Markov operator. A corresponding FORTRAN program can be implemented on a regular personal computer. The calculations result in spectral lineshapes including a complete set of spinning sidebands. The sensitive time scale of the resulting lineshapes depends on the deviation of the sample spinning axis from the magic angle. An example is presented demonstrating the potential of off-magic-angle spinning as a tool to analyze slow tumbling motions. Copyright 1999 Academic Press.