The electronic structure of the uranyl ion

Abstract

The experimental spectra of the uranyl ion, in tetragonal and trigonal equatorial fields, are compared with an empirical model of the excited states arising from four possible configurations of the isolated ion. The data is shown to be explicable only in terms of states originating from σ _u δ _u and σ _u φ _u configurations, although there is evidence for interaction with further configurations. It is argued that the highest energy occupied orbital in the ground state is of σ _u symmetry. The φ _u virtual orbital lies < 3000 cm^-1 above the δ _u virtual orbital in both equatorial fields. Electron-electron repulsion, equatorial field and spin-orbit coupling parameters are derived for Cs₂UO₂Cl₄ and CsUO₂(NO₃)₃. The unique characteristics of the bonding within the uranyl group are discussed.