Investigation of acetylene adsorbed on Cu(100) by multiple-scattering cluster method

Abstract

The carbon K-shell near-edge X-ray absorption fine structure (NEXAFS) spectra of acetylene adsorbed on Cu(100) have been analyzed by the multiple-scattering cluster method. It is identified that the features appearing in the NEXAFS spectra are corresponding to the π∗ and σ∗ resonances as well as the interaction between CH and CC σ∗. Furthermore, it is shown that the Cu(100) substrate acts on the acetylene molecule strongly, which leads to a new feature between the π∗ and σ∗ resonances. It has been found that the molecular plane of C 2H 2 is perpendicular to the surface, but the molecules no longer keep in a line, the hydrogen atoms ascend which make the HCC bond angle around 150°. By a comparison between theory and experiment [1], we found the CC bond length about 1.30 Å and the CC pair adsorbed in a two-fold aligned bridge site.