title: Efficient symmetry-based homonuclear dipolar recoupling of quadrupolar spins: double-quantum NMR correlations in amorphous solids.
abstract: We report novel symmetry-based pulse sequences for exciting double-quantum (2Q) coherences between the central transitions of half-integer spin quadrupolar nuclei in the NMR of rotating solids. Compared to previous 2Q-recoupling techniques, numerical simulations and 23Na and 27Al NMR experiments on Na2SO4 and the open-framework aluminophosphate AlPO-CJ19 verify that the new dipolar recoupling schemes display higher robustness to both radio-frequency field inhomogeneity and to spreads in resonance frequencies. These advances allowed for the first demonstration of 2Q-recoupling in an amorphous solid for revealing its intermediate-range structural features, in the context of mapping 27Al-27Al connectivities between the aluminium polyhedra (AlO4, AlO5 and AlO6) of a lanthanum aluminate glass (La0.18Al0.82O1.5).
authors.affiliation: Physical Chemistry Division, Arrhenius Laboratory, Stockholm University, SE-106 91, Stockholm, Sweden.
authors.forename: Andy Y H
authors.initials: AY
authors.lastname: Lo
authors.forename: Mattias
authors.initials: M
authors.lastname: Edén
mesh_terms: D017607:Aluminum Compounds / Q000737:chemistry*; D003198:Computer Simulation; D005898:Glass / Q000737:chemistry*; D007811:Lanthanum / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D015394:Molecular Structure; D011789:Quantum Theory; D012399:Rotation; D013431:Sulfates / Q000737:chemistry*
chemical_list: D017607:Aluminum Compounds; D013431:Sulfates; C012036:sodium sulfate; D007811:Lanthanum