Identification of C—H resonances in theK-shell excitation spectra of gas-phase, chemisorbed, and polymeric hydrocarbons

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 $X\alpha$ 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.