MULTIPLE-PULSE LINE NARROWING UNDER FAST MAGIC-ANGLE-SPINNING

Combined rotation and multiple-pulse experiments (CRAMPS) are analyzed for the conditions of fast magic-angle spinning, where interference e ffects between both averaging techniques must be considered. Based on this analysis, basic multiple-pulse sequences are adapted to these con ditions. As a new aspect compared with conventional CRAMPS experiments , high-speed MAS also plays an important role in the averaging of resi dual dipolar contributions, that is, high-order correction terms of th e dipolar Hamiltonian. The efficiency in doing this was investigated b y sequences for scaling the dipolar Hamiltonian and by proper homonucl ear decoupling sequences. The resolution of these preliminary experime nts approaches that of conventional CRAMPS experiments, whereas the de mands with respect to spectrometer hardware and tuning are much lower. (C) 1996 Academic Press, Inc.