Simulations of molecular dynamics in solid-state NMR spectra of spin-1 nuclei including effects of CSA- and EFG-terms up to second order

By numerical simulations MAS and QCPMG methods for acquiring spectra of spin-1 nuclei were compared in order to determine the most sensitive experiment for analysis of molecular dynamics. To comply. with the large quadrupolar constants for N-14 and the CSA reported for Li-6 both of these interactions are included up to second order. For H-2 and 6Li both QCPMG and single-pulse MAS experiments were suitable for dynamics studies whereas the single-pulse MAS experiment were the method of choice for investigation of N-14 dynamics for C-Q's larger than 750 kHz at 14.1 T. This property prohibits excitation of the N-14 lineshape using either single hard or softer composite rf-pulses. Focusing on 14N it was demonstrated that the centerband lineshape is sensitive toward both off-MAS and CSA effects. In addition, excitation by real-time pulses showed that proper lineshapes corresponding to a site with a C-Q of 3 MHz may be excited by a very short pulse. (C) 2007 Elsevier Inc. All rights reserved.