Two-Dimensional MAS Multiple-Quantum NMR of Quadrupolar Nuclei. Removal of Inhomogeneous Second-Order Broadening

Abstract
We discuss two modifications to the experiment for removing second-order quadrupolar broadening under MAS conditions recently described by Frydman and Harwood. Pure absorption-mode lineshapes are yielded by both of the new methods. In particular, we demonstrate a novel two-dimensional MAS multiple-quantum experiment in which the spectrum of isotropic frequency shifts can be obtained simply by taking an F₁ projection. Examples of ²³Na NMR results from two different samples are presented.