Inner valence molecular orbitals and structure of the X-ray O-4,O-5(Th,U) emission spectra in thorium and uranium oxides

In the present work, the possibility of an influence of the chemical enviro nment on the structure of O-4,O-5(Th,U) emission spectra of thorium and ura nium oxides was studied. It is noted that the fine structure in such spectr a is caused by the formation of inner valence molecular orbitals, involving relatively deep Th(U) 6p and O(F) 2s atomic orbitals of the neighbouring a toms. This leads to differences between the O-4,O-5(Th,U) emission spectra of ThO2, ThF4, UO2 and gamma-UO3. Also, a comparison between X-ray photoele ctron spectroscopy and X-ray emission spectroscopy data was made for the st udied compounds. This allowed us to conclude that they are in good agreemen t. (C) 1998 Elsevier Science B.V. All rights reserved.