VIBRATIONAL FINE-STRUCTURE IN THE C-1S CORE-LEVEL PHOTOEMISSION OF CHEMISORBED MOLECULES - ETHYLENE AND ETHYLIDYNE ON RH(111)

The origin of fine structure in the core-level photoemission spectra o f the C2H4, C2D4, C2H3 and C2D3 molecules chemisorbed on Rh(111) is pr obed in a careful high-resolution study showing that this structure ar ises from internal molecular vibrations rather than from other chemica lly-shifted carbon atoms. It is shown by comparison of the adsorbate a nd gas-phase spectra that the underlying features are the same despite differences arising from adsorption. This new approach to the investi gation of adsorbed molecules may prove to be useful in further studies of other systems and the possibility that such effects may exist coul d lead to the reinterpretation of other adsorbate systems.