BrK-edge X-ray absorption near edge structure analyses of bromine residue carbon compounds using full multiple-scattering theory

A recent experimental result shows that Br K-edge X-ray absorption near edge structure (XANES) spectra for bromine residue compounds are sensitive to the heat treatment of host carbon compounds. In the present study we attempt to extract useful information on the geometric and electronic structures of these systems by applying a full multiple-scattering approach to XANES analyses. The residue compounds can be classified into three groups on the basis of XANES spectral features. Present detailed analyses provide us some useful information: Group 1, bromine residue compounds are prepared from host carbon compounds heat-treated at 2000-2800 degrees C, where Br(2) molecules exist in the interlayer space of graphite. The interlayer distance expands to about 7.8 angstrom around the Br(2) molecules. For heat treatment at 1900 degrees C, the observed spectra are well explained by the superposition of the spectrum for Group I and that for Group 2, with a ratio of 3 : 4. For Group 2 heat-treated at 1500-1750 degrees C, the host carbon compounds includes Br(-) ions, but no information on the Br(-)(-)C correlation has been obtained. For Group 3 heat-treated at 1000 degrees C, the host carbon compounds mainly includes HBr molecules parallel to small aromatic carbon molecules.