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Broad background bands in Raman spectra of alumina studied by both visible and near‐infrared excitation
Author(s) -
Mortensen A.,
Christensen D. H.,
Nielsen O. Faurskov,
Pedersen E.
Publication year - 1993
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.1250241006
Subject(s) - raman spectroscopy , excitation , excitation wavelength , infrared , analytical chemistry (journal) , visible spectrum , fluorescence , chromium , impurity , spectral line , infrared spectroscopy , chemistry , wavelength , materials science , laser , photochemistry , optics , optoelectronics , physics , organic chemistry , quantum mechanics , astronomy
Raman spectra were obtained for two different samples of alumina. One is usually used as a support for hydro‐treating catalysts in heterogeneous catalysis and the other was synthesized in the laboratory. Different excitation wavelengths were used: 457.9, 488.0, 514.5, 647.1 and 1064 nm. The commercially available alumina showed an intense broad background with excitation in the near‐infrared region, whereas no significant background was observed with visible excitation. The synthetic alumina showed a broad background band with laser excitation in the visible region. It is shown that the appearance of these backgrounds is not due to fluorescent impurities (e.g. iron, chromium or organic compounds). Tentative explanations of the spectral features are provided in terms of density of states (alumina A) or bulk hydroxyl groups (alumina B).