Incomplete double frequency sweeps to select small quadrupolar coupling static powder patterns

Abstract

Difference spectra based on the magnitude of the quadrupolar coupling of a site has been observed under static conditions utilizing a double frequency sweep pulse sequence to enhance the central transition of a small electric field gradient (EFG) environment. Through the use of convergent sweeps that only cover the inner satellite transitions of the smaller EFG site, an echo spectrum results that favors the smaller site, which can then be used in conjunction with normal echo spectra to create a difference spectrum that consists primarily of the smaller site. The simplification of the static lineshape data permits simulation for the extraction of chemical shift anisotropy (CSA) information for the site. The method is demonstrated using 93Nb NMR for samples with multiple niobium environments due to mixtures of compounds, MgNb 2O 6/LiNbO 3, or due to crystallographic structure, KCa 2Nb 3O 10.