title: A 3D experiment that provides isotropic homonuclear correlations of half-integer quadrupolar nuclei.
abstract: Two 3D experiments, capable of producing enhanced resolution two-spin double-quantum (DQ) homonuclear correlations for half-integer quadrupolar nuclei, are described. The first uses a split-t1 MQMAS sequence followed by a sandwiched oR(3) symmetry-based dipolar recoupling sequence to directly excite DQ coherences. In this case an isotropic single-quantum (SQ) coherence starts the homonuclear DQ excitation. In the second experiment a single strong pulse is used to create triple quantum (TQ) coherence followed by a further single pulse conversion to zero-order before a non-sandwiched oR(3) DQ sequence. The first experiment is demonstrated using (87)Rb in RbNO3, with three Rb sites in a ∼5ppm range, and the second to (11)B in caesium triborate, CsB3O5, with two three-coordinated sites separated by ∼2ppm and one four-coordinated boron site. In both cases, all sites are clearly resolved and their connections observed. The second experiment has higher sensitivity and a good signal to noise is obtained in a reasonable time despite the long T1 relaxation time of (11)B in this material.
authors.affiliation: Physics Department, University of Warwick, CV4 7AL Coventry, UK. Electronic address: d.iuga@warwick.ac.uk.
authors.forename: Dinu
authors.initials: D
authors.lastname: Iuga
authors.affiliation: Physics Department, University of Warwick, CV4 7AL Coventry, UK.
authors.forename: Diane
authors.initials: D
authors.lastname: Holland
authors.affiliation: Physics Department, University of Warwick, CV4 7AL Coventry, UK.
authors.forename: Ray
authors.initials: R
authors.lastname: Dupree
mesh_terms: D016880:Anisotropy; D001895:Boron / Q000032:analysis* / Q000737:chemistry*; D007554:Isotopes / Q000032:analysis / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D015203:Reproducibility of Results; D012414:Rubidium Radioisotopes / Q000032:analysis* / Q000737:chemistry*; D012680:Sensitivity and Specificity; D013223:Statistics as Topic
chemical_list: D007554:Isotopes; D012414:Rubidium Radioisotopes; D001895:Boron
keywords: Isotropic homonuclear correlations; MAS; MQMAS; NMR; Quadrupolar nuclei