Аннотация
Using time-dependent high-resolution x-ray photoelectron spectroscopy
at BESSY II, the adsorption and desorption processes of CO on stepped
Pt(355)=Pt5(111)�(111) were investigated. From a quantitative analysis
of C 1s data, the distribution of CO on the various adsorption sites
can be determined continuously during adsorption and desorption.
These unique data show that the terrace sites are only occupied when
the step sites are almost saturated, even at temperatures as low
as 130 K. The coverage-dependent occupation of on-top and bridge
adsorption sites on the (111) terraces of Pt(355) is found to differ
from that on Pt(111), which is attributed to the finite width of
the terraces and changes in adsorbate-adsorbate interactions. In
particular, no long-range order of the adsorbate layer could be observed
by low-energy electron diffraction. Further details are derived from
sticking coefficient measurements using the method devised by King
and Wells Proc. R. Soc. London, Ser. A 339, 245 (1974) and temperature-programmed
desorption. The CO saturation coverage is found to be slightly smaller
on the stepped surface as compared to that on Pt(111). The initial
sticking coefficient has the same high value of 0.91 for both surfaces.
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