Two-Dimensional Solid State NMR and Separation of 7Li Quadrupolar Interactions in Paramagnetic Compounds

In layered paramagnetic compounds, such as La 2 Li 0.5 Ni 0.5 O 4 with a perovskite structure, the 7 Li NMR spectrum is broadened by anisotropic quadrupolar as well as paramagnetic dipolar interactions. We have used a two-dimensional spin echo (SE) experiment to separate the quadrupolar interaction and obtain a clean quadrupolar spectrum along the ω 1 dimension. This is demonstrated in La 2 Li 0.5 B 0.5 O 4 (B = Cu, Ni), through 2D SE experiments conducted in static samples as well as those in spinning at the magic angle. A quadrupole coupling constant of 92 kHz is estimated from the ω 1 spectrum for paramagnetic La 2 Li 0.5 Ni 0.5 O 4 .