Structural studies of molecular and metallic overlayers using angle- resolved photoemission extended fine structure
- Univ. of California, Berkeley, CA (United States)
Angle-resolved photoemission extended fine structure (ARPEFS) was used to study molecular and metallic overlayers on metal surfaces through analysis of p2mg(2x1)CO/Ni(110) and the p(2x2)K/Ni(111) adsorption. For the dense p2mg(2x1)CO/Ni(110) surface layer, photoemission intensities from C 1s level were measured in three directions at photoelectron kinetic energies 60-400 eV. Using multiple-scattering spherical-wave (MSSW) modeling, it was found that CO molecules are adsorbed on short-bridge sites, with adjacent CO along the [110] direction displaced alternatively in opposite directions towards the [001] azimuths to form a zigzag chain geometry. The tilt angle is 16±2° from the surface normal for the direction linking the C atom and the center of the Ni bridge. The carbon C-Ni interatomic distance was determined to be 1.94±0.02Å. The first- to second-layer spacing of Ni is 1.27±0.04Å, up from 1.10Å for the clean Ni(110) surface, but close to the 1.25Å Ni interlayer spacing in the bulk. The C-O bond length and tilt angle were varied within small ranges (1.10--1.20Å and 15--23°) in our MSSW simulations. Best agreement between experiment and simulations was achieved at 1.16Å and 19°. This yields an O-O distance of 2.95Å for the two nearest CO molecules, (van der Waals` radius ~ 1.5 Å for oxygen). Two different partial-wave phase-shifts were used in MSSW, and structural results from both are in very good agreement. For the p(2x2)K/Ni(111) overlayer, ARPEFS {chi}(k) curves from K 1s level measured along [111] and [771] at 130K showed that the K atoms are preferentially adsorbed on the atop sites, in agreement with a LEED study of the same system.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 10110509
- Report Number(s):
- LBL-33040; ON: DE93004700
- Resource Relation:
- Other Information: TH: Thesis (Ph.D.); PBD: Oct 1992
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
36 MATERIALS SCIENCE
NICKEL
SURFACE PROPERTIES
SORPTIVE PROPERTIES
POTASSIUM
ADSORPTION
CARBON MONOXIDE
LAYERS
SURFACES
PHOTOEMISSION
INTERATOMIC DISTANCES
BOND LENGTHS
FOURIER TRANSFORMATION
400201
360104
CHEMICAL AND PHYSICOCHEMICAL PROPERTIES
PHYSICAL PROPERTIES