An X-ray Spectral Study of the Electronic Structure of Uranyl Fluoride UO2F2

The fine structure of the X-ray photoelectron spectrum of low-energy electrons and O4,5(U) X-ray emission spectrum of uranyl fluoride UO2F2 (at binding energies from 0 to 40 eV) was identified on the basis of the electronic structure calculations for the [(UO2)F6]4− cluster with D6h point symmetry, simulating the nearest surrounding of uranium in UO2F2, by the relativistic Xα discrete variation method. It was shown that the U5f electrons can directly participate in chemical bonding, and U6p electrons, in formation of not only inner valence but also outer valence molecular orbitals. The sequence of the inner valence molecular orbitals in the binding energy region from 12 to 40 eV was established, which is essential for development of a procedure for determining the uranium-ligand bond length in the axial direction and in the equatorial plane of the uranyl compounds, based on the characteristics of their X-ray photoelectron spectra.