The electronic structure of thorium monoxide: Ligand field assignment of states in the range 0–5 eV

• Published in: Journal of computational chemistry 2019-01, Vol.40 (2), p.430-446
• Main Authors: Kaledin, Leonid A., Kaledin, Alexey L., Heaven, Michael C.
• Format: Article
• Language: English
• Subjects: actinide electronic structure; Atomic structure; Chemical bonds; Configuration interaction; Electron states; electronic spectroscopy; Electronic structure; Energy levels; Field theory; ligand field theory; Ligands; Mathematical models; Molecular spectra; Nuclear energy; Oxides; Thorium; thorium oxide
• ISSN: 0192-8651; 1096-987X
• DOI: 10.1002/jcc.25710

Configuration interaction ligand field theory (CI LFT) calculations of the electronic energy levels of ThO were performed by treating the molecular electronic states as Th 2+ free‐ion levels perturbed by the ligand field of O2−. Twenty nine experimentally characterized ThO v = 0 energy levels, together with the energy difference between the v = 0 levels of the Y and W states were fitted using a CI LFT model that included Th 2+ 7s 2 , 6d7s, 6d2, 7s7p, 6d7p, 5f7s, and 7p2 configurations. Predictions from these calculations were used to provide tentative assignments for 171 out of 250 ThO band heads listed by Gatterer et al. [“Molecular Spectra of Metallic Oxides”, Specola Vaticana (1957)]. Term energies for 30 electronic states have been determined based on these assignments. Subsequently, the CI LFT model was refined by fitting to a set of 59 electronic term energies. The inclusion of CI effects together with integer valence, atomic‐in‐molecule, ionic bonding ideas reveals atomic energy level patterns that are multiply replicated in the molecular energy level patterns of six Th 2+ O2− atomic ion configurations (6d7s, 6d2, 7s7p, 6d7p, 5f7s, and 7p2) revealing the underlying atomic ion structure that gives rise to the complex and seemingly erratic unassigned bands reported in the Vatican Atlas. © 2018 Wiley Periodicals, Inc. Ligand field theory, used to predict states originating from the Th2+O2- configuration, provide assignments for 20 newly identified electronic states and 108 band systems. The calculations include configuration interaction and define the atomic orbital parentage of the molecular electronic states.