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V Encuentro Sud Americano de Colisiones Inelásticas en la Materia
Electron transfer processes in particle surface interactions.
Vladimir A. Esaulov
Institut des Sciences Moleculaires d’Orsay
CNRS and Université Paris Sud, Orsay 91405, FRANCE
vladimir.esaulov@u-psud.fr
Electron transfer processes play an
important role in adsorption and reactions at
surfaces. Usual surface science experiments deal
with the study of either the kinetics of
adsorption/desorption or with characterisation of
adsorbates or products of reactions in situ.
However the dynamics of the electron transfer
process is usually not studied. I will discuss some
experiments which allow us to obtain this
information by scattering of atoms or ions on a
surface and monitoring the energy and charge
state of the scattered particles. These experiments
allow one to obtain detailed information in
controlled conditions through adequate choices of
initial energy and impact angles and a selection of
final charge state, trajectory (scattering angle) and
energy. Information on electron transfer
probabilities can be obtained for site specific or
surface averaged conditions, mimicking different
approaches of a gas phase particle to a surface.
This quantitative data can serve as a rigorous test
of theoretical models.
observed.
Another example concerns neutralisation
of Li+ ions on Ag and Au clusters supported on
titania (TiO2). Experiments as a function of
growth of clusters an increase in their size have
revealed that much larger neutralisation [4] is
observed on small clusters than on large clusters
or bulk like film.
References
[1] M. Wiatrowski, L. Lavagnino, V.A.
Esaulov Surface Science, Volume 601, 2007,
L39-L43
[2] A R Canário , T Kravchuk and V A Esaulov
2006 New J. Phys. 8 227
[3] M. Casagrande, S. Lacombe, L.
Guillemot, V. A. Esaulov Surface Science,
445, 2000, Pages L29-L35
[4] Ana Rita Canário and V. A. Esaulov, J .
Chem. Phys. 124, 224710 (2006)
Our main interest over the last few years,
has been a study of progressively more complex
cases serving to illustrate effects related to
“promotion” or “poisoning” of reactions in
catalysis and also the size effects. I shall illustrate
our approach for several cases involving a clean
metal surface, a surface with adsorbates and a
nanoscale metal film or cluster supported on a
metal or an oxide. Some of these cases are well
understood but for some substantial theoretical
effort has yet to be made.
As examples I will mention typical results
on negative ion formation for the case of fluorine
negative ion scattering and Li+ neutralisation.
Both involve resonant transfer of electrons. In
case of Li+ ion neutralisation on metals and thin
films recent experiments [1,2] have revealed
“anomalously“ large neutralisation, much larger
than what could be expected in “standard”
models.
The effect of adding controlled amounts
of reactive adsorbates on metals will be illustrated
on the case of chlorine adsorption [3] , where
large changes in electron transfer probabilities are
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