Homonuclear dipolar recoupling under ultra-fast magic-angle spinning: probing 19F-19F proximities by solid-state NMR.
We describe dipolar recoupling methods that accomplish, at high magic-angle spinning (MAS) frequencies, the excitation of double-quantum (DQ) coherences between spin-1/2 nuclei. We employ rotor-synchronized symmetry-based pulse sequences which are either gamma-encoded or non-gamma-encoded. The sensitivity and the robustness to both chemical-shift anisotropy and offset are examined. We also compare different techniques to avoid signal folding in the indirect dimension of two-dimensional double-quantum<-->single-quantum (DQ-SQ) spectra. This comprehensive analysis results in the identification of satisfactory conditions for dipolar (19)F-(19)F recoupling at high magnetic fields and high MAS frequencies. The utility of these recoupling methods is demonstrated with high-resolution DQ-SQ NMR spectra, which allow probing (19)F-(19)F proximities in powered fluoroaluminates.
Wang
Qiang
Q
UCCS, CNRS-8181, Lille-University, 59652, Villeneuve d'Ascq, France; State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Center for Magnetic Resonance, WIPM, Chinese Academy of Sciences, Wuhan 430071, China; Graduate School of the Chinese Academy of Sciences, Beijing, China.
Hu
Bingwen
B
Lafon
Olivier
O
Trébosc
Julien
J
Deng
Feng
F
Amoureux
Jean-Paul
JP
D000465:Algorithms; D003198:Computer Simulation; D005462:Fluorine Radioisotopes; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D015233:Models, Statistical
D005462:Fluorine Radioisotopes