The Erected Dipole Model in the Adsorption of Cesium on Fluorinated Molybdenum
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
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Interest in power-producing thermionic diodes containing both electropositive and electronegative additives has lead to studies of the structure of adsorbed layers. One of the models advanced to describe this layer is that of the erected dipole, in which polar molecules are erected on a surface by a strong surface electric field. Published evidence for this structure in the case of some adsorbates, namely, barium oxide and cesium chloride, is reviewed. A modified version of the erected dipole model, presented in this report, was used to analyze published data for the system cesium on fluorinated molybdenum. The results are compared with data in the literature and suggest that cesium fluoride molecules are adsorbed as erected dipoles in this system. The effect of this configuration on work function for the system cesium on fluorinated molybdenum as temperature is raised is discussed. Also discussed is the strength of the electric field associated with the surface, which is responsible for the erection of the dipoles.
- Properties of Metals and Alloys