Sensitivity enhancement in MAS NMR of half-integer quadrupolar nuclei using sideband selective double-frequency sweeps

Sensitivity enhancement of the NMR signal of the half-integer spin quadrupolar nuclei under magic angle spinning (MAS) conditions is demonstrated using the DFS (Double Frequency Sweep) enhancement scheme. It has been shown, both through numerical simulations and by experiments, that with a sinusoidal amplitude profile a narrow band DFS scheme performs much better than a DFS scheme with a large bandwidth. The total enhancement compares favorably to the hyperbolic secant (HS) pulse scheme under MAS. Finally, we report the robustness of this DFS scheme with respect to variation of different experimental parameters, making it a very attractive choice for acquiring sensitivity-enhanced NMR experiments of half-integer quadrupolar nuclei. © 2011 Published by NRC Research Press.