Probing the electronic structure and Au–C chemical bonding in AuC2− and AuC2 using high-resolution photoelectron spectroscopy

Abstract

We report photoelectron spectroscopy (PES) and high-resolution PE imaging of AuC2(-) at a wide range of photon energies. The ground state of AuC2(-) is found to be linear (C∞v, (1)Σ(+)) with a …8π(4)4δ(4)17σ(2)9π(4)18σ(2) valence configuration. Detachments from all the five valence orbitals of the ground state of AuC2(-) are observed at 193 nm. High-resolution PE images are obtained in the energy range from 830 to 330 nm, revealing complicated vibronic structures from electron detachment of the 18σ, 9π, and 17σ orbitals. Detachment from the 18σ orbital results in the (2)Σ(+) ground state of neutral AuC2, which, however, is bent due to strong vibronic coupling with the nearby (2)Π state from detachment of a 9π electron. The (2)Σ(+)-(2)Π vibronic and spin-orbit coupling results in complicated vibronic structures for the (2)Σ(+) and (2)Π3/2 states with extensive bending excitations. The electron affinity of AuC2 is measured accurately to be 3.2192(7) eV with a ground state bending frequency of 195(6) cm(-1). The first excited state ((2)A') of AuC2, corresponding to the (2)Π3/2 state at the linear geometry, is only 0.0021 eV above the ground state ((2)A') and has a bending frequency of 207(6) cm(-1). The (2)Π1/2 state, 0.2291 eV above the ground state, is linear with little geometry change relative to the anion ground state. The detachment of the 17σ orbital also results in complicated vibronic structures, suggesting again a bent state due to possible vibronic coupling with the lower (2)Π state. The spectrum at 193 nm shows the presence of a minor species with less than 2% intensity relative to the ground state of AuC2(-). High-resolution data of the minor species reveal several vibrational progressions in the Au-C stretching mode, which are assigned to be from the metastable (3)Π2,1,0 spin-orbit excited states of AuC2(-) to the (2)Π3/2,1/2 spin-orbit states of neutral AuC2. The spin-orbit splittings of the (3)Π and (2)Π states are accurately measured at the linear geometry. The current study provides a wealth of electronic structure information about AuC2(-) and AuC2, which are ideal systems to investigate the strong Σ-Π and spin-orbit vibronic couplings.

The design and construction of a high-resolution velocity-map imaging apparatus for photoelectron spectroscopy studies of size-selected clusters

“…29 Our high-resolution imaging study of Au 2 − achieved a vibrational temperature of ∼175 K. 20 Dimer anions are especially challenging to cool in our laser vaporization source because we cannot achieve long enough resident time in the nozzle due to ion loss. We have recently observed a vibrational temperature of 125 K for AuC 2 − , 23 whereas for Au 4 − we were able to essentially eliminate all vibrational hot bands by using the helium carrier gas seeded with 5% Ar in combination with an optimal resident time. 21…”

“…(3) for small R or low energy electrons. [20][21][22][23] Furthermore, the calibration parameter a increases essentially linearly with the voltage applied to the repeller plate (V R ). With our current geometry (a 50 cm distance between the interaction zone and the imaging detector plane), the constant a is 3.720 × 10 −6 for V R = −300 V, and for KE in eV and R in μm.…”

“…It has been fully tested and has yielded some very interesting initial results. [20][21][22][23] The new VMI system is based on a previous photoion-imaging strategy that highlight how weak fields in the electrostatic lenses during the initial acceleration stage allow achieving a better velocity focusing at the cost of sacrificing temporal focusing. 24 Our new VMI system can reach a resolution of 1.2 cm −1 for near threshold electrons comparable to that reported by Neumark, 16 while still maintaining good energy resolution ( KE/KE ∼ 0.53%) for higher energy electrons comparable to that reported by Cavanagh and co-workers.…”

Gas phase anion photoelectron spectroscopy and theoretical investigation of gold acetylide species

“…: +86 10 62635054, Fax: +86 10 62563167. microwave (FTMW) spectroscopy. 22 The photoelectron spectra of AuC 2 , 23,24 AuC 3 H , 25 and AuC 4 H 26 as well as those of AuC n and AuC n H (n = 2, 4, and 6) 27 were measured using electron velocity map imaging (VMI) technique. The photoelectron spectra and bonding properties of LAuC 2 H (L = Cl, I, and C 2 H) were investigated using the magnetic-bottle anion photoelectron spectroscopy experiment and theoretical calculations.…”

Aurocarbons: Binary Gold Carbides, Binary Carbon Aurides and their Derivatives

“…Particularly well understood from the vantage point of quantitative measurements are gaseous C 2 Au and the corresponding anion 22 . The ground state of C 2 Au (X 2 Σ + ) has been shown by photoelectron spectroscopy to be linear but only ca 0.2 kJ mol −1 lower in energy than the bent first excited state (A ′2 π).…”