Analysis of multiple pulse NMR in solids. III

Abstract

A 52‐pulse cycle recently introduced in a communication, which has a substantially increased resolving power compared to previously available techniques, is analyzed in detail. Also, a new 24‐pulse cycle which is essentially equivalent to the 52‐pulse cycle in resolving power is introduced. These pulse cycles achieve their enhanced resolution compared to the REV‐8 cycle by removing the effects of the homonuclear dipolar interaction in solids to higher orders of magnitude without reintroducing any dipolar terms eliminated by REV‐8. Principles of pulse cycle decoupling are introduced which greatly simplify the systematic development of compound multiple pulse cycles. Beginning with the 2‐pulse solid echo sequence, we show how these principles could have been used in designing the WAHUHA and REV‐8 cycles and the 14‐pulse cycle recently introduced by Haeberlen. We further demonstrate the application of this method by developing several new pulse cycles such as a 12‐pulse cycle equivalent to the 14‐pulse cycle, the 24‐pulse cycle, and the 52‐pulse cycle. Finally, proton chemical shift tensor components for several organic solids which were measured using the 52‐pulse cycle are reported without detailed discussion.