The interaction of oxygen with the iron (111) surface,mainly studied by AES

The cleaned surface was oxidized by means of pure oxygen at a pressure of 3 × 10⁻⁶ – 3 × 10⁻³ pa and at temperatures of 300 K, 370 K, and 620 K. The Auger peaks of high energy (for oxygen at 510 eV and for iron at 703 eV) were used for the quantitative determination of the oxygen coverage on the iron surface. The experimental results on the change of oxygen coverage as a function as a function of the dose are interpreted by means of a theoretical model and provided definite informations about the bonding state of the adsorbate. In the lower energy part of the Auger spectrum there appear peak shape modifications during oxidation. These observations allow us to suppose that in the process of oxidation there are in action two kinds of chemical bonding of oxygen with iron differing by density of states in the valence band.