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Near-Infrared Spectrum of the First Excited State of Au₂.

ABSTRACT: Au₂ ⁺ is a simple but crucial model system for understanding the diverse catalytic activity of gold. While the Au₂ ⁺ ground state (X² Σ_g ⁺ ) is understood reasonably well from mass spectrometry and computations, no spectroscopic information is available for its first excited state (A² Σ_u ⁺ ). Herein, we present the vibrationally resolved electronic spectrum of this state for cold Ar-tagged Au₂ ⁺ cations. This exceptionally low-lying and well isolated A² Σ_(u) ⁺ ←X² Σ_(g) ⁺ transition occurs in the near-infrared range. The observed band origin (5738 cm^-1 , 1742.9 nm, 0.711 eV) and harmonic Au-Au and Au-Ar stretch frequencies (201 and 133 cm^-1 ) agree surprisingly well with those predicted by standard time-dependent density functional theory calculations. The linearly bonded Ar tag has little impact on either the geometric or electronic structure of Au₂ ⁺ , because the Au₂ ⁺ ⋅⋅⋅Ar bond (∼0.4 eV) is much weaker than the Au-Au bond (∼2 eV). As a result of 6 s←5d excitation of an electron from the antibonding σ_u ^* orbital (HOMO-1) into the bonding σ_g orbital (SOMO), the Au-Au bond contracts substantially (by 0.1 Å).

SUBMITTER: Forstel M

PROVIDER: S-EPMC8596823 | biostudies-literature | 2021 Nov

REPOSITORIES: biostudies-literature

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Near-Infrared Spectrum of the First Excited State of Au2.

Förstel Marko M Pollow Kai K Studemund Taarna T Dopfer Otto O

Chemistry (Weinheim an der Bergstrasse, Germany) 20210915 61

Au2 + is a simple but crucial model system for understanding the diverse catalytic activity of gold. While the Au2 + ground state (X2 Σg + ) is understood reasonably well from mass spectrometry and computations, no spectroscopic information is available for its first excited state (A2 Σu + ). Herein, we present the vibrationally resolved electronic spectrum of this state for cold Ar-tagg ...[more]

PMID: 34423877

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Near-Infrared Spectrum of the First Excited State of Au₂.

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Near-Infrared Spectrum of the First Excited State of Au<sub>2</sub>.

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