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Research Highlights
Nicholas Camillone
Ultrafast Surface Dynamics Group Research:
• Testing The “Pseudo-Thermal” Model: CO Desorption from Pd
Because the (√3 × √3)R30° phase of carbon monoxide binds tightly to the
(111) surface of Pd, it is a useful model system for testing the
“pseudo-thermal” description of ultrafast photoinduced desorption. We
have performed detailed measurements and modeling of the ultrafast
photodesorption dynamics that indicate that the desorption is activated
as in conventional thermal desorption. Further, we find that the same
activation energy for desorption describes both the ultrafast and
thermal (slow) processes.
…more »
• Adsorption State Dependent Reaction Dynamics: O2 Desorption
from Pd
We have investigated the adsorption-state-dependence of the substrate–adsorbate
coupling responsible for the desorption of molecularly chemisorbed
oxygen from the Pd(111) surface. By varying the amount of O2
on the surface we sequentially populated three adsorption states and
measured their photoinduced desorption dynamics. Our model for the
energy transfer from the surface to the adsorbate reveals that the more
tightly bound the molecules are, the more efficient the
electron-mediated energy transfer process.
…more »
• Efficient Ultrafast Photoinduced Bimolecular Chemistry: CO Oxidation
on Pd
As a step closer to the goal of time-resolving surface chemical reaction
events, we have investigated the ultrafast photoinduced reaction of CO
with atomic oxygen on the Pd(111) surface. Under UHV conditions Pd is an
excellent thermal catalyst. We have found the ultrafast photoinduced
oxidation also to be very efficient; the oxidized fraction of the
desorbed molecules ranges from ~15% to 40%, approximately an order of
magnitude greater than observed from Ru(001) under similar conditions.
We also find that the dynamics are strongly dependent on the initial CO
coverage in a manner consistent with an activation energy that depends
on the initial CO binding site. Our results are consistent with the
photooxidation occurring rapidly (within one to several picoseconds)
from an initial mixed CO+O adlayer structure without time for
diffusional phase segregation.
…more »
Chemical Imaging Group Research:
• Manipulation of and Desorption from TiO2 surfaces
Stay tuned for new developments.
• Hot carrier dynamics
Stay tuned for new developments.
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