Spectroscopic study on the adsorption and dissociation of CH3I on Pd(100): thermal and photo effects

Frigyes Solymosi, Károly Révész

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54 Citations (Scopus)


The adsorption of methyl iodide on a Pd(100) surface has been investigated by temperature programmed desorption (TPD), work function change Δφ, ultraviolet and X-ray photoelectron (UPS and XPS) spectroscopies at 85-425 K. By means of TPD only one adsorption state is identified, Tp = 129 K, which is formed only at high exposures and attributed to multilayer. Adsorption of CH3I is characterized by a significant decrease in the work function (1.54 eV at monolayer) indicating that adsorbed CH3I has a positive outward dipole moment. UPS, XPS and TDS measurements suggest that CH3I adsorbs dissociatively at submonolayer even at 85-90 K yielding adsorbed CH3 and I species. The dissociation of the monolayer is complete below 200 K. This process is accompanied by a decrease in the binding energy of the I(3d 5 2) core electrons. The decomposition of adsorbed CH3 started above 160 K and is completed below 250 K. The primary product of the decomposition is CH4 which desorbs with Tp = 170 K. C2H6, C2H4 and H2 were detected only in trace amounts. Illumination of the adsorbed layer at 85-90 K enhanced the extent of the dissociation which is ascribed to the generation of photoelectrons.

Original languageEnglish
Pages (from-to)38-49
Number of pages12
JournalSurface Science
Issue number1-2
Publication statusPublished - Jan 1 1993

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Materials Chemistry

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