K. Anic, A. Bukhtiyarov, H. Li, Ch. Rameshan, G. Rupprechter:
"CO Adsorption on Reconstructed Ir(100) Surfaces from UHV to mbar Pressure: A LEED, TPD, and PM-IRAS Study";
Journal of Physical Chemistry C, 120 (2016), 20; S. 10838 - 10848.

Kurzfassung englisch:
ABSTRACT: Clean and stable surface modifications of an iridium (100) single crystal,
i.e., the (1 ◊ 1) phase, the (5 ◊ 1) reconstruction, and the oxygen-terminated (2 ◊ 1)-O
surface, were prepared and characterized by low energy electron diffraction (LEED),
temperature-programmed desorption (TPD), infrared reflection absorption spectroscopy
(IRAS) and polarization modulation IRAS (PM-IRAS). The adsorption of CO in
UHV and at elevated (mbar) pressure/temperature was followed both ex situ and in situ
on all three surface modifications, with a focus on mbar pressures of CO. The Ir(1 ◊ 1)
surface exhibited c(4 ◊ 2)/c(2 ◊ 2) and c(6 ◊ 2) CO structures under low pressure
conditions, and remained stable up to 100 mbar and 700 K. For the (2 ◊ 1)-O
reconstruction CO adsorption induced a structural change from (2 ◊ 1)-O to (1 ◊ 1), as
confirmed by LEED, TPD, and IR. For Ir (2 ◊ 1)-O TPD indicated that CO reacted
with surface oxygen forming CO2. The (5 ◊ 1) reconstruction featured a reversible and
dynamic behavior upon CO adsorption, with a local lifting of the reconstruction to (1 ◊
1). After CO desorption, the (5 ◊ 1) structure was restored. All three reconstructions
exhibited CO adsorption with on-top geometry, as evidenced by IR. With increasing CO exposure the resonances shifted to
higher wavenumber, due to adsorbate−adsorbate and adsorbate−substrate interactions. The largest wavenumber shift (from
2057 to 2100 cm−1) was observed for Ir(5 ◊ 1) upon CO dosing from 1 L to 100 mbar.

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