Photoelectron spectra of the decomposition of ethylene on (110) tungsten

Photoelectron spectra, LEED patterns, and work function changes were obtained for ethylene adsorbed on (110) tungsten at room temperature, and with subsequent heat treatment. For saturated adsorption of C₂H₄ on (110) W at room temperature, features in the photoelectron spectrum were observed which are believed to be due to the C, HCC, and Cmetal bonds in an adsorbed species of the form C₂H₂. The work function decreased by 1.2 eV at saturation, but LEED showed no change from the clean surface pattern. Upon heating to ≈ 500 K, where hydrogen is known to desorb, the CH bond was broken, whereas the CC and Cmetal bonds remained. The work function increased, from saturation, by ≈ 0.6 eV and the LEED pattern exhibited a large diffuse background with no new spots. Upon heating to ≈ 1100 K the CC bond broke and the LEED pattern ordered into the characteristics carbon contamination pattern.