UV/HREELS measurements of the excited states of adsorbed CO: benchmarks for ab initio calculations

• Published in: Surface science 1999-01, Vol.419 (2), p.144-149
• Main Authors: Ford, L.P, Blowers, P, Chen, N.C, Lee, I.C, Masel, R.I
• Format: Article
• Language: English
• Subjects: Ab initio quantum chemical calculations; Applied sciences; Carbon monoxide; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electron energy loss spectroscopy; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Exact sciences and technology; Impurity and defect levels; energy states of adsorbed species; Metals. Metallurgy; Physics; Platinum; Surface and interface electron states; UV-spectroscopy; UV/HREELS
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/S0039-6028(98)00773-0

Recently there has been some controversy about CO adsorption on platinum, with some researchers supporting the Blyholder model and others saying that corrections are needed. We have used UV/HREELS to examine the electronic structure of adsorbed CO to distinguish between the various models. We have found that the 5σ to 2π ∗ triplet peak shifts from 6.2 to 5.6 eV upon adsorption while the 5σ to 2π ∗ singlet peak shifts from 8.3 to 8.2 eV. Both peaks also broaden, as expected from the Blyholder model. A comparison of these results to previous calculations shows that only Hückel calculations predict a shift that is within 0.5 eV of the experimental shift. Most of the previous calculations predict shifts that are in the wrong direction.