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Author Diaz, J. ♦ Anders, S. ♦ Zhou, X. ♦ Moler, E. J. ♦ Kellar, S. A. ♦ Hussain, Z.
Sponsorship (US)
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Publisher American Physical Society (APS)
Language English
Subject Keyword CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS ♦ ABSORPTION ♦ ABSORPTION SPECTRA ♦ ATOMS ♦ BINDING ENERGY ♦ CARBON ♦ CHEMICAL BONDS ♦ PHOTOEMISSION ♦ PROBES ♦ SPECTRA
Abstract The same method used to determine Σ<sup>*</sup> excitations in the x-ray-absorption spectra of organic molecules is applied to analyze the structure of the Σ<sup>*</sup> band in the x-ray absorption spectra of amorphous carbon (a-C) films. The analysis assumes that only a Σ bond interaction to first neighbors is relevant to explain the structure of the Σ<sup>*</sup> band in a-C films. This is justified by the local character of the x-ray absorption probe and the short- range order existing in these films. The identification of the different Σ<sup>*</sup> components is based on the dependence of the Σ<sup>*</sup> binding energy with bond distance. The Σ<sup>*</sup> band is built up by summing the components resulting from the possible different types of Σ bonds in a-C. This method serves to separate the π<sup>*</sup> states from the Σ<sup>*</sup> states and to identify the kind of chemical bonds existing between carbon atoms. This analysis yields a proportion of sp³-bonded atoms of 60% in a film with a density of about 2.9 g/cm³, which is a value closer to what is expected from theoretical calculations. The analysis identifies a component at about 288.5 eV which is associated to strained Σ bonds of the type of the existing in sp{sup 3} bonded rings like cyclopropene. Raman and photoemission spectroscopies help in the interpretation of the x-ray absorption spectra and the assignment of the Σ<sup>*</sup> components.
ISSN 01631829
Educational Use Research
Learning Resource Type Article
Publisher Date 2001-09-15
Publisher Department Lawrence Berkeley National Laboratory
Publisher Place United States
Journal Physical Review, B: Condensed Matter
Volume Number 64
Issue Number 12
Technical Publication No. LBNL/ALS-43609
Organization Lawrence Berkeley National Laboratory


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