Symmetry principles for the design of radiofrequency pulse sequences in the nuclear magnetic resonance of rotating solids

Some new symmetry theorems are presented which simplify the task of designi ng multiple-pulse radio-frequency pulse sequences in magic-angle-spinning s olid-state NMR. The symmetry theorems apply to sequences denoted RNnv which consists of N repetitions of a pulse sequence element R, alternating in ph ase between the values +/- pi v/N. Each R element ideally rotates the spins by an angle pi about the rotating frame x-axis. The entire RNnv sequence i s timed to span n rotational periods. Applications are presented for homonu clear double-quantum and zero-quantum recoupling, heteronuclear decoupling and heteronuclear recoupling. (C) 2000 Elsevier Science B.V. All rights res erved.