Strong configuration interaction in $$ {\mathbf{UBr}}_6^{2 - } $$ and $$ {\mathbf{UCl}}_6^{2 - } $$ molecular complexes

Abstract

The Stark structure of U4+ ion multiplets in $$ {\mathrm{UBr}}_6^{2 - } $$ and $$ {\mathrm{UCl}}_6^{2 - } $$ molecular complexes were analyzed in an approximation of weak and anomalously strong configuration interactions taking into account the influence of excited configurations with charge transfer. It was shown that application of a modified crystal field theory in the approximation of an anomalously strong configuration interaction considerably improved the agreement between theory and experiment. Based on experimental data on the Stark structure, covalence parameters were first estimated for U4+–Br– and U4+–Cl–. A readily computer-implemented technique is offered to estimate parameter errors in the theory describing the experimental results. Using this technique, the errors of parameters $$ {\mathrm{B}}_0^4,\;{\mathrm{B}}_0^6 $$ , γof, γrf, ∆c1, ∆c2, and ∆c3 were calculated for a crystal field Hamiltonian obtained in the approximation of an anomalously strong configuration interaction.