LEED and resonance EELS study of the (NO) 2 dimer on graphite

• Published in: Surface science 1995-05, Vol.329 (3), p.184-192
• Main Authors: Nandhakumar, I.S., Li, Z.Y., Palmer, R.E., Amos, R.
• Format: Article
• Language: English
• Subjects: Ab initio quantum chemical methods and calculations; Condensed matter: structure, mechanical and thermal properties; Electron energy loss spectroscopy; Exact sciences and technology; Graphite; Low energy electron diffraction (LEED); Nitrogen oxides; Physical adsorption; Physics; Solid surfaces and solid-solid interfaces; Surface structure and topography; Surface structure, morphology, roughness, and topography; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties)
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/0039-6028(95)00061-5

The structure of physisorbed (NO) 2 films on graphite has been investigated using resonance electron energy loss spectroscopy in conjunction with low energy electron diffraction (LEED). Various ordered phases were resolved for the first time by the LEED technique as a function of coverage. Transient negative ion resonance formation was manifested in strong enhancements of the ν = 0−1 vibrational cross section in the incident electron energy range 11–16 eV. A splitting of this resonance by 2.6 ± 0.2 eV indicates formation of the dimer configuration on the surface. The resonance splitting was observed for all adsorbate coverages studied. Detailed angular distributions have been recorded, which showed distinct features for different adsorbed phases. Ab initio self-consistent field calculations allow a qualitative analysis of the orientation of the NO dimer. Our results are consistent with an orientation of the NO dimer plane approximately parallel to the surface in the γ phase and perpendicular in the β phase.