Core level electron energy-loss spectra of minerals: pre-edge fine structures at the oxygen K-edge |
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| Authors: | P A van Aken B Liebscher V J Styrsa |
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| Institution: | Institut für Mineralogie, Technische Universit?t Darmstadt, Schnittspahnstra?e 9, D-64287 Darmstadt, Germany e-mail: vanaken@hrz1.hrz.tu-darmstadt.de, DE
Institut für Mineralogie, Universit?t Frankfurt, Senckenberganlage 28, D-60054 Frankfurt, Germany, DE
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| Abstract: | In a recent paper entitled “Water in minerals detectable by electron energy-loss spectroscopy EELS” by R. Wirth, it has been
claimed that OH–- and H2O-bearing minerals exhibit a characteristic peak in the ELNES spectra at about 528 eV prior to the onset of the O K-edge at 532 eV, which could be used for (semi-)quantitative determination of water- or OH-contents on a nanometer scale.
It is shown here by parallel electron energy-loss spectroscopy (PEELS) recorded in a transmission electron microscope (TEM)
that O K-pre-edge peaks with very high intensities may also exist in water-free compounds and minerals, in particular when they contain
transition metals. These spectral features arise from covalent mixing of the metal and oxygen states, which introduces oxygen
p character in unoccupied states of mainly metal character. The point is illustrated by the comparison of hematite (α-Fe2O3) and lepidocrocite (γ-FeOOH) O K-edge PEELS spectra which exhibit similar intensities of the pre-edge peak, despite of their grossly different OH– contents. As a consequence, the general validity of the method proposed by Wirth is questioned.
Received: 4 December 1997 / Revised, accepted: 22 April 1998 |
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