Adlayer structure dependent ultrafast desorption dynamics in carbon monoxide adsorbed on Pd (111)
Sung-Young Hong1, Pan Xu2, Nina R Camillone1
1Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973, USA.
The Journal of Chemical Physics
|July 11, 2016
Summary
Ultrafast desorption reveals how carbon monoxide (CO) binding sites on palladium affect energy transfer. CO coverage influences binding sites, impacting desorption probability and energy transfer rates, with implications for surface chemistry.
Area of Science:
- Surface Science
- Physical Chemistry
- Materials Science
Background:
- Understanding substrate-adsorbate interactions is crucial for catalysis and surface reactions.
- Carbon monoxide (CO) adsorption on transition metals like palladium is a fundamental system in surface science.
Purpose of the Study:
- Investigate the coverage dependence of substrate-adsorbate energy transfer for CO on Pd(111).
- Elucidate the relationship between CO adsorption site population and ultrafast photoinduced desorption dynamics.
Main Methods:
- Ultrafast photoinduced desorption experiments.
- Two-pulse correlation spectroscopy to measure adsorbate-substrate energy transfer rates.
- Phenomenological modeling of frictional coupling and electron-mediated energy transfer.
Main Results:
- CO adsorption site population shifts with coverage: threefold hollows, then bridge/near bridge, finally mixed threefold hollow/top sites.
- Desorption probability increases significantly with coverage (0.24-0.75 ML).
- Adsorbate-substrate energy transfer rate shows non-monotonic behavior with a minimum at intermediate coverages.
Conclusions:
- Adsorption site-dependent electron-mediated energy coupling strength (ηel) decreases in the order: threefold hollow > bridge/near bridge > top site.
- Weakening of ηel moderates the rise in desorption probability.
- Enhanced energy transfer at saturation is attributed to interadsorbate transfer from hollow to top sites.
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