Identification of the Lower Transitions in the Spectra of Uranyl Complexes

The typical low‐energy spectra of the uranyl complexes—both in solution and in the solid state—are interpreted by using group theory and qualitative molecular orbital theory. A comparative study of the effects of ligation on the spectrum shows that the observed facts can be rationalized by means of only one possible identification scheme. The band system situated at 20 000–22 000 cm⁻¹ is due to a ${}^1{\Sigma }_g^{+}{\mathrm{\hspace{0.17em}\to \hspace{0.17em}}}^1{\Phi }_g$ transition, while the band system at 22 500–27 000 cm⁻¹ is due to a ${}^1{\Sigma }_g^{+}{\mathrm{\hspace{0.17em}\to \hspace{0.17em}}}^1{\Delta }_g$ transition.