High temperature photoelectron spectroscopy: A study of U, UO, and UO2

The He i photoelectron spectrum of atomic uranium has been recorded in the vapor phase. Bands associated with metal (6d)−1, (7s)−1, and (5f)−1 ionizations were observed. The relative intensities of the (6d)−1 and (5f)−1 bands are consistent with computed relative cross sections at the He i energy, whereas the intensity of the (7s)−1 band is larger than expected from computed cross sections, implying enhancement of this feature by autoionization effects. HeI photoelectron spectra have also been recorded for the vapor above a heated equimolar UO2(s):U(s) mixture. By studying the spectra obtained as a function of temperature, bands associated with UO and UO2 were identified and these were assigned using relativistic Hartree–Fock–Slater calculations on these molecules.