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Two‐dimensional nutation echo 75 As NQR spectroscopy in antiferroelectric NH 4 H 2 AsO 4 using the maximum entropy method
Author(s) -
Kątowski P.,
Maćkowiak M.
Publication year - 1995
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1260331016
Subject(s) - nutation , chemistry , laser linewidth , electric field gradient , nuclear magnetic resonance , spectroscopy , tensor (intrinsic definition) , pulse sequence , crystallite , analytical chemistry (journal) , nuclear quadrupole resonance , physics , atomic physics , quadrupole , optics , crystallography , mathematics , laser , astronomy , quantum mechanics , chromatography , pure mathematics
With a view to developing efficient methodologies for the evaluation of the asymmetry parameter of the electric field gradient (EFG) tensor from polycrystalline specimens, an alternative approach which involves two‐dimensional spin‐echo NQR data processing by the maximum entropy method (MEM) is presented. The superiority of MEM over the traditional fast Fourier transform (FFT) method is demonstrated by the analysis of two‐dimensional NQR data obtained using the modified pulse sequence. The method has been successfully applied to the determination of the EFG tensor at the 75 As site in the antiferroelectric phase of polycrystalline ammonium dihydrogenarsenate (ADA), where conventional nutation spectroscopy fails owing to the large NQR linewidth.