Role of Spin-Orbital Splitting of 5f-Orbitals of Uranium Atom in the Formation of Its Chemical State

摘要

Chemical shifts (ChSh) of nine emission lines of the uranium L-series in uranium oxides UO_(2+x) (x = 0-1) with respect to UO_2 were studied by using a precise crystal-diffraction X-ray spectrometer and the changes in energy of spin-orbital splitting (SOS) - Δδnl_(+-) of inner nl-orbitals of the uranium atom were calculated from the data of ChSh of spin-doublet lines. For UO_(2+x) oxides, a linear decrease in Δδnl_(+-) values with increasing degree of uranium oxidation was found. On the basis of the comparison of experimental Δδnl_(+-) values with Dirac-Hartree-Fock atomic calculations, it was concluded that the observed variations in Δδnl_(+-) values are due to the redistribution of electron and spin density between the 5f_(7/2)- and 5f_(5/2)-levels of the fine structure of the uranium atom without changes in atomic charge state.