Total electron yield (TEY) efficiency of sp2 and sp3 carbon atoms in the TEY-X-ray absorption near-edge structure (XANES) of 1,4,7,10-alkyltetracenes.

X-ray absorption near-edge structure (XANES) in the CK region of 1,4,7,10-alkyltetracenes, which are composed of sp2-C atoms in the tetracene ring and sp3-C atoms in the alkyl-chains, are measured using the total electron yield (TEY) and theoretically analyzed by DFT calculations to quantitatively investigate the π* and σ* peak intensities in the TEY-CK-XANES. The calculated π*/σ* peak intensity ratios are well approximated by the linear functions passing through the origin as a function of the sp2-C fraction, which is expressed as sp2-C/(sp2-C + sp3-C). In contrast, the measured π*/σ* peak intensity ratios are well approximated by curve functions passing through the origin, considering the TEY efficiency between sp2-C and sp3-C. The approximated curve functions indicate that the TEY efficiency of sp3-C is lower than that of sp2-C even in molecules. This confirms that the TEY efficiency of sp2-C and sp3-C should be considered in quantitative discussions on the sp2-C and sp3-C fractions from TEY-CK-XANES of carbon materials.

Relationship between Width and Height of π* Peak in C K-XANES of Graphitic Carbons.

The relationship between the width and height of the π* peak on X-ray absorption near edge structure (XANES) in the C K region of graphitic carbons is investigated from XANES measurements and theoretical analysis. This relationship is herein named the "characteristic diagram of π* peak profile". Mechanically ground (MG) graphite experimentally exhibits a linear correlation on the diagram. To understand the linear correlation, C K-XANES of the graphitic hexagonal carbon layers are calculated using first-principles calculations by focusing on the edge carbon atoms. The linear correlation is well explained by the ratio of the edge carbon atoms of the graphitic hexagonal carbon layers. The characteristic diagram of π* peak profile is applied to industrial carbon black (CB) for identification. CBs exhibit identical distributions on the diagram, which depend on their uses. It is therefore confirmed that the proposed characteristic diagram of π* peak profile can be a useful tool to identify graphitic carbons from the edge carbon atoms.