Clean and Oxygen Exposed Potassium Studied by Photoelectron Spectroscopy

Clean evaporated potassium films have been studied in a combined UV-X-ray photoelectron instrument. The valence band and the K 3 p 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 Al K α 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 1 s 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 O 2 . For comparison spectra from a sample exposed to about 45 L H 2 O were recorded.