Raman scattering from phonons and electronic excitations in UO2 with different oxygen isotopes

Comparison of the phonons and electronic excitations of UO2 with different oxygen isotopes (16O, 18O), two purely electronic excitations at 4162 and 5778 cm−1 have been evidenced by their limited shift, when 16O is replaced by 18O. The bands observed at 570, 1144 and 2300 cm−1 in U16O2 shift to 545, 1091 and 2190 cm−1 for U18O2. The wavenumbers and the isotope shifts of these bands exhibit multiple relationships. It supports the assignments of the 1LO (~570 cm−1) and 2LO (~1144 cm−1) phonons for U16O2. Both bands exhibit marked decrease for increasing O/U ratio. The observed phenomenon is regarded as a good estimation of the stoichiometry of a uranium oxide. In addition, by analyzing the intensity ratios of the 2LO to 1LO phonons for various UO2 samples, the 2LO band is assigned to the Fröhlich interaction. Defect‐induced and/or deformation potential mechanisms play a dominant role for the 1LO band. Copyright © 2015 John Wiley & Sons, Ltd. The phonons and electronic excitations of UO2 with different oxygen isotopes (16O, 18O) have been measured. Two purely electronic excitations at 4162 and 5778 cm−1 have been evident by the limited shifts, when 16O is replaced by 18O. In addition, the bands observed at 570, 1144 and 2300 cm−1 in U16O2 shifts to 545, 1091 and 2190 cm−1 for U18O2. These bands exhibit multiple relationships and nearly the same isotope shifts ratio. It supports the assignments of the 1LO (~570 cm−1) and 2LO (~1144 cm−1) phonons for U16O2. Both of the bands exhibit marked decrease for O/U increasing and can be regarded as a good estimation of the stoichiometry of a uranium oxide. Their origins are discussed. The 2LO band is assigned to the Fröhlich interaction. Defect‐induced and/or deformation potential mechanisms play a dominant role for the 1LO band.