| Abstract
| - The electronic structure and chemical bonding in the Ta3− cluster are investigated using photoelectron spectroscopy and density functional theory calculations. Photoelectron spectra are obtained for Ta3− at four photon energies: 532, 355, 266, and 193 nm. While congested spectra are observed at high electron binding energies, several low-lying electronic transitions are well resolved and compared with the theoretical calculations. The electron affinity of Ta3 is determined to be 1.35 ± 0.03 eV. Extensive density functional calculations are performed at the B3LYP/Stuttgart +2f1g level to locate the ground-state and low-lying isomers for Ta3 and Ta3−. The ground-state for the Ta3− anion is shown to be a quintet (5A1′) with D3h symmetry, whereas two nearly isoenergetic states, C2v (4A1) and D3h (6A1′), are found to compete for the ground-state for neutral Ta3. A detailed molecular orbital analysis is performed to elucidate the chemical boding in Ta3−, which is found to possess multiple d-orbital aromaticity, commensurate with its highly symmetric D3h structure.
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