Mobility of CO on the (110) plane of Tungsten |
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Authors: | J.-R. Chen R. Gomer |
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Affiliation: | The Departments of Physics and Chemistry and The James Ranck Institute, The University of Chicago, Chicago, Illinois 60637, USA |
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Abstract: | The measurement of time autocorrelation functions of field emission current fluctuations has been applied to the adsorption of CO on the (110) plane of tungsten. For molecularly adsorbed virgin-CO, no evidence for diffusion was found at any coverage, although a weak, exponentially decaying correlation function, suggesting flip-flop between differing ad-sites, was seen. A hysteresis in the mean square fluctuation could be clearly identified with conversion to β-CO. For the latter state a flip-flop signal was seen for 280 ? T ? 650 K, and for T650 K a correlation function corresponding to diffusion was found. The activation energy of diffusion was 23 kcal, independent of coverage. This value agrees closely with that found for oxygen diffusion at = 0.5. For CO readsorbed on a β-layer (α-CO) neither diffusion nor flip-flop was seen. |
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