Two-dimensional solid state NMR and separation of Li-7 quadrupolar interactions in paramagnetic compounds

Ln layered paramagnetic compounds, such as La2Li0.5Ni0.5O4 with a perovskit e structure, the Li-7 NMR spectrum is broadened by anisotropic quadrupolar as well as paramagnetic dipolar interactions. We have used a two-dimensiona l spin echo (SE) experiment to separate the quadrupolar interaction and obt ain a clean quadrupolar spectrum along the wi dimension. This is demonstrat ed in La2Li0.5B0.5O4 (B = Cu, Ni), through 2D SE experiments conducted in s tatic samples as well as those in spinning at the magic angle. A quadrupole coupling constant of 92 kHz is estimated from the Wi spectrum for paramagn etic La2Li0.5Ni0.5O4.