A critical interpretation of the near-edge X-ray absorption fine structure of chemisorbed benzene

Abstract

Near-edge X-ray absorption fine structure (NEXAFS) measurements for submonolayer benzene coverages on Ag(110) are reported and interpreted in light of recent electronic structure calculations for free benzene. Quantitative analysis of the continuum resonances indicates that benzene is bound parallel to Ag(110) while analysis of the C(1s) → π ∗ (e 2u) transition intensities yields a maximum tilt of ~ 10–15°. The apparent tilting suggested by the π ∗ resonances is most likely not a real and global tilt, but probably arises from the presence of tilted minority species. A comparison of the NEXAFS spectra for benzene on Ag(110) with those previously reported for benzene on Pt(111) and Mo(110) and phenyl thiolate on Mo(110) indicates that strong adsorbate-substrate interactions may result in significant perturbations in the bound-state region of the near-edge structure, as well as shifting of the continuum resonances due to changes in intramolecular bond lengths.