Gibbsite difference spectra

The As-HAO system presents special difficulties for IR and XAFS spectroscopic analysis. In an XAFS spectrum, the magnitude of peaks in the Fourier transformed EXAFS spectrum is a function of several variables, two of which are atomic number (z) and distance from the central As atom. With only half as many electrons as Fe, the scattering power of Al is weak, therefore peaks representing As-Al scattering in the Fourier-transformed EXAFS are smaller and more difficult to interpret. IR and Raman spectra of As(V) sorbed on gibbsite are difficult to interpret for an entirely different reason substantial overlap of peaks representing Al(V)-0/Al-OH vibrations and As(V)-0/As(V)-OH vibrations (Myneni et al, 1998). 

In order to study the structure of anionic forms in more detail (including lithium localization) we carried out NMR investigations of LiCl-2Al(0H)3 l.5H20 obtained by the interaction of lithium chloride with gibbsite, as well as the product of its dehydration LiCl-2Al(OH)3. The best description of the experimental peak shape in Al NMR spectrum of gibbsite Al(OH)3 (with the mean square difference between the experimental and calculated spectra of approx. 5%) was obtained with the use of superposition of two lines of identical intensity described by the parameters ... 

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