Coadsorption of Cs and CO on Ru(001)

Formation of Cs + CO islands and isotope exchange of the CO located inside the islands

Hiroshi Kondoh, H. Orita, H. Nozoye

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

The CO adsorption on Cs-covered Ru(001) surfaces has been studied by means of temperature-programmed desorption (TPD), low-energy electron diffraction (LEED), high-resolution electron energy loss spectroscopy (HREELS) and X-ray photoelectron spectroscopy (XPS). When CO molecules adsorb on the Cs-preadsorbed surfaces at 85 K, two-dimensional Cs + CO islands are formed for Cs coverages lower than 0.25, which exhibit p(2 × 2) LEED patterns irrespective of both Cs and CO coverages. The p(2 × 2) Cs + CO island has an almost constant [CO]:[Cs] stoichiometry of 2:1 at Cs coverages below 0.2. This stoichiometry changes to 4:3 when the islands cover the whole surface (θCs = 0.25). The local density of Cs in the island is 0.25 independent of Cs coverage. The C-O stretching frequency of the CO species located outside the island shifts from 2075 to 2000 cm-1 in proportion to Cs coverage. The C-O stretching mode of the inside CO species appears at much lower frequencies (1800-1580 cm-1), which depend on the [CO]:[Cs] ratio. The former and the latter frequency shifts are associated with a weak long-range and a strong short-range effect of Cs, respectively. The isotope exchange between the isotope-labeled CO species occurs exclusively inside the islands. The temperature onset of the isotope-exchange reaction is estimated to be 450-500 K. This is comparative to the temperature onset of the desorption from the 2:1 state, while it is lower by 100 K than that from the 4:3 state, which results in a distinct difference in the exchange fraction for these states. The formation mechanism of the p(2 × 2) Cs + CO island is discussed based on the recently proposed models of the alkali + CO coadsorption process.

Original languageEnglish
Pages (from-to)8790-8798
Number of pages9
JournalJournal of Physical Chemistry
Volume99
Issue number21
Publication statusPublished - 1995
Externally publishedYes

Fingerprint

Isotopes
Low energy electron diffraction
isotopes
Stoichiometry
Stretching
Electron energy loss spectroscopy
Alkalies
Temperature programmed desorption
Diffraction patterns
Desorption
X ray photoelectron spectroscopy
Adsorption
Temperature
Molecules
stoichiometry
electron diffraction
desorption
frequency shift
temperature
alkalies

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

Coadsorption of Cs and CO on Ru(001) : Formation of Cs + CO islands and isotope exchange of the CO located inside the islands. / Kondoh, Hiroshi; Orita, H.; Nozoye, H.

In: Journal of Physical Chemistry, Vol. 99, No. 21, 1995, p. 8790-8798.

Research output: Contribution to journalArticle

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