DOUBLE-ROTATION NMR, MAGIC-ANGLE-SPINNING NMR, AND X-RAY-DIFFRACTION STUDY OF THE STRUCTURE OF ALUMINUM MOLYBDATE

An Al-27 NMR study of aluminum molybdate (Al2(MoO4)3) has been carried out. Using the double-rotation technique (DOR), the residual line bro adening observed in magic angle spinning (MAS) that is caused by secon d-order quadrupolar interactions is completely removed. The four inequ ivalent aluminum resonances, as predicted from the space group symmetr y obtained from X-ray and neutron powder diffraction data, are clearly revealed by NMR. Moreover, additional structure in the DOR spectrum m ay be indicative of further inequivalency in the unit cell that is not discernible by powder diffraction methods. Tentative assignments of t he observed aluminum resonances are given.