Electronic excitation of uranium atoms sputtered from uranium metal and oxides


Atoms sputtered from solids by energetic ion irradiation often partition across electronically excited states. We developed a resonance ionization method to measure the population of the uranium 5K5 state (620 cm−1) relative to the 6L6 ground state for atoms sputtered from metallic and oxide surfaces. A considerable fraction of sputtered atoms reside in the 5K5 state, and the fraction increases as the surface oxidizes. The effect is consistent across uranium metal, UO2, and U3O8, and is invariant with the departing velocity of the sputtered atom. The data are not sufficient to determine the excitation mechanism, however they are qualitatively consistent with resonant electron transfer from the surface to the departing atom.

Spectrochimica Acta Part B: Atomic Spectroscopy