Auger electrons, definition

A variety of model catalysts have been employed we start with the simplest. Single-crystal surfaces of noble metals (platinum, rhodium, palladium, etc.) or oxides are structurally the best defined and the most homogeneous substrates, and the structural definition is beneficial both to experimentalists and theorists. Low-energy electron diffraction (LEED) facilitated the discovery of the relaxation and reconstruction of clean surfaces and the formation of ordered overlayers of adsorbed molecules (3,28-32). The combined application of LEED, Auger electron spectroscopy (AES), temperature-programmed desorption (TPD), field emission microscopy (FEM), X-ray and UV-photoelectron spectroscopy (XPS, UPS), IR reflection... 

It also includes Auger electron spectroscopy microprobe identification of the surface crud in the pit, or definition of the surface composition gradient previously omitted from the speculation on atom transport processes. 

The definition of the powder surfaces tends to be in terms of the process for making it (23). This limits interpretation of their properties and also limits generalization of properties to surfaces which have been generated by atmospheric corrosion. Conversely, the LEED, Auger electron spectroscopy, photo emission properties, etc, are measured on fresh surfaces in UHV, because interpretation is difficult for more complex configurations and because experience has shown that these properties are profoundly modified and confused by exposure to real atmospheres. 

For definitions of acronyms, see Table XII. [From Thompson, M., Baker, M. D., Christie, A., and Tyson, J. F. (1985). Auger Electron Spectroscopy, Wiley-Interscience, New York.]... 

We conclude, therefore, that the momentum of the electron in its orbit within the atom does not affect the direction of ejection in the way demanded by the theory of Auger and Perrin. While this does not constitute definite evidence against the physical reality of electronic orbits, it is a serious difficulty for the conception. 

Better spatial definition can be attained using transmission microscopy but the opaqueness of the electrode support negates its effectiveness. The spatial distribution of elements on the surface can be resolved with a scanning Auger microprobe. The problem of electron beam damage to the modified surface has prevented widespread usage. 

Some topics have been omitted from this review. This holds for the structure and function of metal sites in metalloproteins and metalloenzymes in relation to enzymatic catalysis, for which the reader is referred to Cramer and Hodgson (68) and Doniach et al. (80). Also, chemisorption studies and the structure of adsorbate-covered surfaces are not considered in this review, which deals with XAES in transmission, thus characterizing bulk material. It is noted that even in the case of chemisorbed atoms XANES data analysis requires physically the definition of clusters of considerable size. On the other hand, the analysis is simplified for adsorbed molecules. Very pronounced near-edge effects (usually obtained by electron-stimulated Auger measurements) are observed for low-Z-atom(C, N, O, F>containing chemisorbed... 

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