H-1 decoupling with third averaging in solid NMR

We show that appropriate modulation of the rf amplitude in the two-pulse ph ase-modulation (TPPM) H-1 decoupling sequence provides an appreciable impro vement in the decoupling efficiency. The effect of the amplitude modulation on TPPM is examined using the average Hamiltonian theory, and the improvem ent in the decoupling efficiency is ascribed to third averaging. Improved d ecoupling is demonstrated with C-13 magic-angle spinning (MAS) NMR in glyci ne and uniformly C-13, N-15-labeled glycylisoleucine. (C) 2001 Elsevier Sci ence B.V. All rights reserved.