Identification of C—H resonances in the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>K</mml:mi></mml:math>-shell excitation spectra of gas-phase, chemisorbed, and polymeric hydrocarbons

Abstract

We demonstrate the existence and angular dependence of C---H resonances in the carbon $K$-shell excitation spectra of hydrocarbons. Near-edge x-ray-absorption fine-structure spectra of oriented polyethylene chains exhibit pronounced resonances which are associated with C---C and C---H bonds as determined from their angular dependence and from $X\ensuremath{\alpha}$ multiple-scattering calculations. The presence of C---H resonances is also found in $K$-shell excitation spectra of free ethylene and ethylene chemisorbed on various metal surfaces.