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  Zamudio-Bayer, V.; Hirsch, K.; Langenberg, A.; Lawicki, A.; Terasaki, A.; von Issendorff, B.; Lau, J.T.: Electronic ground states of Fe₂⁺ and Co₂⁺ as determined by x-ray absorption and x-ray magnetic circular dichroism spectroscopy. The Journal of Chemical Physics 143 (2015), p. 244318/1-6

10.1063/1.4939078
Open Access version by external provider

Abstract:
The ⁶Π electronic ground state of the Co₂⁺ diatomic molecular cation has been assigned experimentally by x-ray absorption and x-ray magnetic circular dichroism spectroscopy in a cryogenic ion trap. Three candidates, ⁶Φ, ⁸Φ, and ⁸Γ, for the electronic ground state of Fe₂⁺ have been identified. These states carry sizable orbital angular momenta that disagree with theoretical predictions from multireference configuration interaction and density functional theory. Our results show that the ground states of neutral and cationic diatomic molecules of 3d transition elements cannot generally be assumed to be connected by a one-electron process.