Vibrational analysis of the C 1s photoemission spectra from pure ethylidyne and ethylidyne coadsorbed with carbon monoxide on Rh(111)

Abstract

High-resolution core-level photoemission with a resolution better than the intrinsic width of the C 1s level has been used to study pure and coadsorbed ethylidyne overlayers on Rh(111). Components due to excitation of the CH stretch vibration are clearly resolved in the C 1s spectra. In addition, a component due to the CC vibration of the ethylidyne molecules is identified. The asymmetry parameter is found to be similar for the two carbon atoms of the C 2H 3 molecule, indicating similar densities of states at the Fermi level for the two atoms. Coadsorption of ethylidyne with CO is found to induce a large C 1s binding-energy shift of the outer carbon atom of the ethylidyne. The remaining lineshape parameters, including the energy splits and intensity ratios of the CH vibrational progressions, are similar for the pure and coadsorbed ethylidyne.