[en] The adsorption of methyl iodide as well as of molecular iodine on uranium metal and on uranium dioxide has been studied at 25⁰C. Surfaces of the substrates were cleaned and characterized before and after exposure using X-ray photoelectron (XPS) and X-ray and electron induced Auger electron (AES) spectroscopy. Exposures amounted up to 1500 L CH₃I on uranium metal, 1000 L CH₃I on UO₂, 100 L I₂ on uranium metal, and 75 L I₂ on UO₂ (1 L = 1 Langmuir = 10^-6 torr x sec). From the measured binding energies, Auger parameters, and intensity ratios for substrate and adsorbate constituents we deduced that for both CH₃I and I₂ on uranium metal a uranium iodide, UI₃, is formed. The adsorption of CH₃I on U-metal is in addition accompanied by the formation of a carbide-type carbon, UC. Thus, in both cases a dissociative (adsorption/reaction) process is observed. For adsorption of CH₃I on UO₂ the experimental findings indicate a dissociative process, too, though the species formed could not be identified. In contrast, I₂ adsorption on UO₂ appears to have non-dissociative character. Saturation coverages for CH₃I were found to be approx.= 2 L on U-metal and approx.= 5 L on UO₂, for I₂ approx.= 40 L on U-metal and 10-15 L on UO₂. Variations in the iodine Auger kinetic energy and in the Auger parameter are interpreted in light of extraatomic relaxation processes. (orig.)