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The electronic structure of the Au2+ cation is essential for understanding its catalytic activity. We present the optical spectrum of mass‐selected Au2+ measured via photodissociation spectroscopy. Two vibrationally resolved band systems are observed in the 290–450 nm range (at ca. 440 and ca. 325 nm), which both exhibit rather irregular structure indicative of strong vibronic and spin‐orbit coupling. The experimental spectra are compared to high‐level quantum‐chemical calculations at the CASSCF‐MRCI level including spin‐orbit coupling. The results demonstrate that the understanding of the electronic structure of this simple, seemingly H2+‐like diatomic molecular ion strictly requires multireference and relativistic treatment including spin‐orbit effects. The calculations reveal that multiple electronic states contribute to each respective band system. It is shown that popular DFT methods completely fail to describe the complex vibronic pattern of this fundamental diatomic cation. [ABSTRACT FROM AUTHOR]

Innentitelbild: The Optical Spectrum of Au2+ (Angew. Keywords: cations; electronic structure calculations; gold; optical spectroscopy; photodissociation EN cations electronic structure calculations gold optical spectroscopy photodissociation 21434 21434 1 11/18/20 20201123 NES 201123 B Das erste optische Spektrum von Au SB 2 sb SP + sp b , das durch elektronische Photodissoziation erzeugt wurde, wird in der Zuschrift auf S. 21587 von M. Förstel, R. Mitric, O. Dopfer und Mitarbeitern mit quantenchemischen Rechnungen analysiert. Cations, electronic structure calculations, gold, optical spectroscopy, photodissociation. [Extracted from the article]

The electronic structure of the Au2+ cation is essential for understanding its catalytic activity. We present the optical spectrum of mass‐selected Au2+ measured via photodissociation spectroscopy. Two vibrationally resolved band systems are observed in the 290–450 nm range (at ca. 440 and ca. 325 nm), which both exhibit rather irregular structure indicative of strong vibronic and spin‐orbit coupling. The experimental spectra are compared to high‐level quantum‐chemical calculations at the CASSCF‐MRCI level including spin‐orbit coupling. The results demonstrate that the understanding of the electronic structure of this simple, seemingly H2+‐like diatomic molecular ion strictly requires multireference and relativistic treatment including spin‐orbit effects. The calculations reveal that multiple electronic states contribute to each respective band system. It is shown that popular DFT methods completely fail to describe the complex vibronic pattern of this fundamental diatomic cation. [ABSTRACT FROM AUTHOR]