A novel dipolar dephasing method for the slow magic angle turning experiment

Complete suppression of the resonances from protonated carbons in a slow ma gic angle spinning experiment can be achieved using five dipolar dephasing (Five-DD) periods distributed in one rotor period. This produces a spectrum containing only the spinning sidebands (SSB) from the nonprotonated carbon s. It is shown that the SSB patterns corresponding to the nonprotonated car bons are not distorted over a wide range of dipolar dephasing times. Hence, this method can be used to obtain reliable principal values of the chemica l shift tensors for each nonprotonated carbon. The Five-DD method can be re adily incorporated into isotropic-anisotropic 2D experiments such as FIREMA T and 2D-PASS to facilitate the measurement of the C-13 chemical shift tens ors in complex systems. (C) 2001 Academic Press.