Vibrational and electronic spectroscopy of pyridine and benzene adsorbed on the Rh(111) crystal surface
We report the vibrational and electronic spectra for pyridine and benzene adsorbed on the Rh(111) crystal surface obtained by high-resolution electron energy loss spectroscopy (HREELS). Low-energy electron diffraction (LEED), thermal desorption spectroscopy (TDS), and optical second harmonic generation (SHG) have also been used to provide complementary information. Pyridine adsorption on Rh(111) was studied over the 77--450 K temperature range. At 77 K, multilayers of pyridine are observed with a vibrational spectrum similar to that of liquid pyridine. Between 185 and 230 K, HREELS and TDS indicate that both physisorbed and chemisorbed pyridine species are present on the surface. The physisorbed species desorbs at 295 K, while the chemisorbed species is stable until it decomposes on the surface at 400 K. We propose that the chemisorbed species is an ..cap alpha..-pyridyl complex as thermal desorption spectroscopy indicates partial dehydrogenation of this pyridine surface species. Electronic energy loss spectra for both benzene and pyridine adsorbed at 310 K show only a weak transition centered at approx.4 eV. The absence of prominent ..pi --> pi..* transitions, which are readily observed for multilayers of benzene adsorbed on Rh(111), implies that the ..pi.. orbitals are strongly involved in the chemisorption bond of these molecules with the Rh(111) surface.
- Research Organization:
- Materials and Chemical Sciences Division, Lawrence Berkeley Laboratory, Department of Chemistry, University of California, Berkeley, California 94720
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 5616026
- Journal Information:
- J. Chem. Phys.; (United States), Vol. 88:1
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
BENZENE
CHEMISORPTION
DESORPTION
ELECTRON SPECTROSCOPY
PYRIDINES
RHODIUM
SORPTIVE PROPERTIES
ADSORPTION
ELECTRON DIFFRACTION
AROMATICS
AZINES
CHEMICAL REACTIONS
COHERENT SCATTERING
DIFFRACTION
ELEMENTS
HETEROCYCLIC COMPOUNDS
HYDROCARBONS
METALS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PLATINUM METALS
SCATTERING
SEPARATION PROCESSES
SORPTION
SPECTROSCOPY
SURFACE PROPERTIES
TRANSITION ELEMENTS
400201* - Chemical & Physicochemical Properties