Nuclear Magnetic Resonance and Quadrupole Coupling in Hydrous and Anhydrous Sodium Molybdate and Sodium Tungstate Spinel

Publisher Website
Google Scholar
Abstract
The nuclear magnetic resonance of 23Na in powder samples of hydrous and anhydrous sodium molybdate and sodium tungstate has been investigated. The anhydrous compounds crystallize in the cubic spinel of type H11, Fd3m presumably with ionic charges of 1 + and 6 + on the metals. The 23Na quadrupole couplings are the largest yet observed for this nucleus and have values of 2.62 and 2.48 MHz in the molybdate and tungstate respectively, as determined from both first- and second-order effects on the magnetic resonance spectrum. These couplings have negligible temperature dependences. Using charges of 1 + and 6 + for the metal ions, assuming that the oxygens are in their ideal positions in the spinel structure and neglecting any contributions from oxygen dipoles and quadrupoles, the electric field gradient was calculated to be 12 × 1013 e.s.u./cm3, in good agreement with the experimental gradient of 7.5 × 1013 e.s.u./cm3. Preliminary measurements of the sodium spin–lattice relaxation time, using tone-burst techniques, indicated a value between 30–60 s. The 95.97Mo nuclear resonances were also observed in the molybdate and these resonances showed no quadrupole effects.

This publication has 0 references indexed in Scilit: