The adsorption of methyl iodide on uranium and uranium dioxide: Surface characterization using X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES)

The adsorption of methyl iodide on uranium and on uranium dioxide has been studied at 25 °C. Surfaces of the substrates were characterized before and after adsorption by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). The XPS binding energy results indicate that CH₃I adsorption on uranium yields a carbide-type carbon, UC, and uranium iodide, UI₃. On uranium dioxide the carbon electron binding energy measurements are consistent with the formation of a hydrocarbon, —CH₃-type moiety. The interpretation of XPS and AES spectral features for CH₃I adsorption on uranium suggest that a complex dissociative adsorption reaction takes place. Adsorption of CH₃I on UO₂ occurs via a dissociative process. Saturation coverage occurs on uranium at approximately two langmuir (1 L = 10^?6 Torr s) exposure whereas saturation coverage on uranium dioxide is found at about five langmuir.