Energy Levels of U4+ in an Octahedral Crystalline Field

The electronic energy levels determined from absorption spectra of U⁴⁺ in crystals containing UCl₆^2— complexes are identified as to irreducible representation and the resulting set of levels used to determine the least‐squares best values of Slater F_k integrals, spin—orbit ζ_5f, and fourth‐ and sixth‐degree crystalline potential parameters A 〈r⁴〉 and B 〈r⁶〉. It was necessary to diagonalize within the 5f² configuration all these interactions simultaneously. The values are $F_2{\text{=191.4,F}}_4{\text{=33.83,F}}_6{\text{=3.98,ζ}}_{\text{5f}}{\text{=1796,A〈r}}^4{\text{〉=912,B〈r}}^6\text{〉=56.5}$ . New data on the spectra of the UBr₆^2— complex are presented.