Anomalous adsorption kinetics. γ-Nitrogen on the {110} plane of tungsten
- 1 January 1979
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases
- Vol. 75, 2100-2115
- https://doi.org/10.1039/f19797502100
Abstract
This study extends previous work on nitrogen adsorption on tungsten single crystal planes on the [001] zone to the {110} plane at low temperatures. The functional dependence of the sticking probability s on coverage at crystal temperatures between 90 and 120 K shows anomalous behaviour, in that (a) the initial sticking probability is low (0.22) by comparison with the expectation from other planes on the [001] zone and (b)s increases with coverage to a maximum at around half the saturation coverage. Desorption from this plane indicates a γ(molecular) state desorption peak temperature of ≈ 190 K. The results are compared with kinetic data from other planes on the [001] zone and a simple kinetic model is proposed, which accounts for the major features of the sticking probability profiles. On a second {110} crystal evidence was found for significant β(dissociative) state formation, attributable either to the presence of impurities or steps on this crystal. Changes of secondary electron yield with coverage in the γ state are found to be complex, in contrast to work function changes.Keywords
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