Molecular ethylene adsorption on Rh(111) and Rh(100): estimation of the C-C stretching force constant from the surface vibrational frequencies
Molecular ethylene adsorption on Rh(111) and Rh(100) between 90 and 200 K has been studied by thermal desorption spectroscopy (TDS), low-energy electron diffraction (LEED), and high-resolution electron energy loss spectroscopy (HREELS). The HREEL vibrational spectra for molecularly adsorbed ethylene on these surfaces are interpreted by using the Dewar-Chatt-Duncanson model for ethylene coordination to metal atom(s); gas-phase ethylene and gauche 1,2-dibromoethane are used to model the coordination extremes. It is shown that the traditional CH/sub 2/ functional group modes are coupled in adsorbed ethylene and do not adequately describe the normal modes of vibration. However, the C-C stretching force constant in adsorbed ethylene can be estimated from the deuteriated ethylene vibrational frequencies, and a general correlation between deuteriated vibrational frequency and adsorbed C-C force constant is proposed. Using this correlation together with empirical correlations between force constant and bond length derived for gas-phase molecules, they estimate C-C bond orders of 1.5 and 1.2 for ethylene adsorbed on Rh(111) and Rh(100), respectively. These results indicate that on both surfaces chemisorbed ethylene is strongly distorted from its gas-phase geometry.
- Research Organization:
- Lawrence Berkeley Lab., CA (USA)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 6046668
- Journal Information:
- J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 92:16; ISSN JPCHA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400201* -- Chemical & Physicochemical Properties
ALKENES
COHERENT SCATTERING
DATA
DIFFRACTION
ELECTRON DIFFRACTION
ELECTRON SPECTROSCOPY
ELEMENTS
ENERGY LEVELS
ENERGY-LOSS SPECTROSCOPY
ETHYLENE
EXCITED STATES
EXPERIMENTAL DATA
HYDROCARBONS
INFORMATION
METALS
MILLER INDICES
NORMAL-MODE ANALYSIS
NUMERICAL DATA
ORGANIC COMPOUNDS
PLATINUM METALS
RHODIUM
SCATTERING
SORPTION
SORPTIVE PROPERTIES
SPECTROSCOPY
SURFACE PROPERTIES
TRANSITION ELEMENTS
VIBRATIONAL STATES