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Collision induced migration of adsorbates on surfaces L. Romm and M. Asscher

Summary: Collision induced migration of adsorbates on surfaces
L. Romm and M. Asscher
Department of Physical Chemistry and Farkas Center for Light Induced Processes,
The Hebrew University, Jerusalem, 91904, Israel
Y. Zeiri
Department of Chemistry, Nuclear Research Center, Negev, P.O.B. 9001, Beer-Sheva, Israel
Received 11 January 1999; accepted 17 March 1999
Collision induced migration CIM has been identified as a new surface phenomenon and has been
studied for the first time using molecular dynamics simulations. The CIM process was represented
by an energetic gas phase argon atom, striking an adsorbed nitrogen molecule on Ru 001 . The
efficiency of CIM was investigated as a function of the collider initial kinetic energy and angle of
incidence. It was found that at low coverages an adsorbed molecule can migrate more than 150
following collisions at high energies and grazing angles of incidence. As coverage increases,
inter-adsorbate collisions result in significant reduction of migration distances. At high energies, the
competing process of collision induced desorption becomes dominant, leaving behind molecules
which migrate shorter distances. These competing channels lead to a collision energy for which
CIM is maximized. For the N2 /Ru system, the CIM process is most effective near collider energy
of 2.0 eV. This new surface phenomenon of CIM has to be considered for better understanding the
full range of surface processes which govern industrial high pressure catalysis. At the tail of the
thermal kinetic energy distribution, energetic colliders from the gas phase lead to CIM and generate


Source: Asscher, Micha - Institute of Chemistry, Hebrew University of Jerusalem


Collections: Chemistry