Quadrupole Coupling and Anisotropic Shielding from Single-Crystal NMR of the Central Transition for Quadrupolar Nuclei.87Rb NMR of RbClO4and Rb2SO4

The possibility of retrieving parameters for the combined effect of quadrupole coupling and small chemical-shielding anisotropies from single-crystal NMR of the central transition for half-integer quadrupolar nuclei has been successfully investigated.⁸⁷Rb single-crystal NMR of RbClO₄and Rb₂SO₄serve as two properly chosen and illustrative examples. Thereby, discrepancies between some of the⁸⁷Rb parameters recently reported for these two interactions in powders of RbClO₄and Rb₂SO₄, and determined from MAS and static powder NMR, have been clarified. The orientations of the crystallographic axes for the two rubidium crystals have been predicted by the NMR results and verified independently by XRD analysis.