Study on the behavior of oxygen atoms in swift heavy ion irradiated CeO2 by means of synchrotron radiation X-ray photoelectron spectroscopy

To study the effects of swift heavy ion irradiation on cerium dioxide (CeO2), CeO2 sintered pellets were irradiated with 200 MeV Xe ions at room temperature. For irradiated and unirradiated samples, the spectra of X-ray photoelectron spectroscopy (XPS) were measured. XPS spectra for the irradiated samples show that the valence state of Ce atoms partly changes from +4 to +3. The amount of Ce3+ state was quantitatively obtained as a function of ion-fluence. The relative amount of oxygen atom displacements, which are accompanied by the decrease in Ce valence state, is 3–5%. This value is too large to be explained in terms of elastic interactions between CeO2 and 200 MeV ions. The experimental result suggests the contribution of 200 MeV Xe induced electronic excitation to the displacements of oxygen atoms.