Clean and Oxygen Exposed Potassium Studied by Photoelectron Spectroscopy

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Abstract
Clean evaporated potassium films have been studied in a combined UV-X-ray photoelectron instrument. The valence band and the K 3p level were studied using 21.2 and 40.8 eV radiation. In the 40.8 eV excited spectrum a structure attributed to surface and volume plasma losses was resolved. Using AlKα excitation the binding energies of the core levels in potassium were determined. Potassium films at a temperature of 77 K were exposed to oxygen at a pressure of about 10-5 Pa for increasing time periods. The intensity and shape of the core levels as well as of the valence band were studied after each exposure. The shapes of the O 1s line and the valence band excited by 40.8 eV radiation were followed as a function of increasing temperature after an initial exposure of 45 L O2. For comparison spectra from a sample exposed to about 45 L H2O were recorded.