“Molecular Clusters” on the Surface of an Oxidizing Metal
FIELD ion microscopy, which holds the possibility of resolving the individual atoms in a metallic surface, should in principle be a powerful tool for the study of reactions on surfaces. As part of an extensive study of the mechanism of oxidation of several metals, we have recently observed the formation of characteristic, reproducible, small clusters of atoms of regular shape when a perfect iridium surface is exposed to oxygen.
The nature of adsorbed oxygen on rhodium, palladium and gold electrodes
Summary Oxygen coverage has been determined on rhodium, palladium and gold anodes as a function of potential and time. The oxygen-containing film consists of chemisorbed oxygen atoms, but phase oxide can nucleate and grow under severe conditions of anodization. A basis for distinguishing between chemisorption and phase formation is presented. Comparison with previous work on platinum allows the stoichiometry of chemisorbed oxygen at coverage steps and limiting coverage regions to be determined. This stoichiometry can be utilized for accurate measurement of real surface area of rhodium and palladium electrodes.
Evaporation of Metal Crystals
A mechanism for vaporization of solid metals involving monatomic ledges on metal crystal surfaces is deduced, and an equation is derived for evaporation rate in terms of the dynamics of these ledges. It is shown that crystal edges are a ready source for monatomic ledges. The limiting expression for the vaporization coefficient of large, perfect crystals is given as a function of pressure and temperature by α=⅔(p/pe)+⅓, where pe is the equilibrium vapor pressure. Various predictions of this theory are compared with available experimental results.