Abstract
The kinetics of the adsorption system CO/Pt(111) has been studied
by time-resolved high-resolution x-ray photoelectron spectroscopy
using third generation synchrotron radiation at BESSY II. CO is dosed
by a supersonic molecular beam device which allows for a high sample
pressure (here up to 10�6 mbar) and a fast switching of the pressure.
The site-specific occupation of CO adsorbed on on-top and bridge
sites is determined quantitatively from C 1s spectra, which can be
taken with a minimum collection time of 1.5 s per spectrum. Based
on the observation of thermal equilibrium between the two sites,
we perform a phenomenological analysis of the data, assuming a constant
binding energy difference DeltaE. From the on-top/bridge occupation
ratio as a function of coverage obtained by uptake measurements we
extract a value of DeltaE = 41 meV. With the same ansatz, DeltaE
is calculated from temperature-dependent measurements at a constant
coverage. Finally, determination of the coverage during isothermal
desorption is used to obtain the total binding energy of CO on Pt(111).
Differences between our evaluation methods and literature reports
are discussed.
Users
Please
log in to take part in the discussion (add own reviews or comments).