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1677667 
Journal Article 
Sticking probability measurement in a reactive system 
Berenbak, B; Butler, DA; Riedmuller, B; Papageorgopoulos, DC; Stolte, S; Kleyn, AW 
1998 
1 
Surface Science
ISSN: 0039-6028 
414 
1-2 
271-278 
WOS:000076198200029 
The sticking probability of reactive molecules on surfaces is usually measured using the well-established beam reflectivity technique of King and Wells. The fundamental problem of this technique results from the interaction of the gas with the walls of the chamber. For the majority of gases used in King and Wells' sticking probability measurements, the exposure of the chamber walls to the gas causes changes in the effective pumping speed of the vacuum chamber.



A simple model is presented which shows the influence of the residence rime of particles on the walls on the effective pumping speed of the system. In combination with lest data, this model reveals a very symmetric response to changes in the beam flux. This insight is used to develop a straightforward method for the determination of the initial sticking coefficient S-o, which allows for changes in pumping speed.



In applying the technique to the adsorption of NO on Ru(0001), the initial sticking coefficient is observed to be very high (S-o> 0.9) and almost constant for incident energies between 0.3 eV <E-t<2.5 eV, suggesting more than one dissociation pathway. For the Ru(0001)-(1 x 1)H surface, S-o increases from 0.2 to 0.6 in the same energy :range, indicating a partially activated process. (C) 1998 Elsevier Science B.V. All rights reserved. 
chemisorption; hydrogen; metallic surfaces; molecule solid reactions; nitrogen oxides; ruthenium; single crystal surfaces; solid-gas interfaces; sticking