Probing the electronic and vibrational structure of Au₂Al₂⁻ and Au₂Al₂ using photoelectron spectroscopy and high resolution photoelectron imaging

The electronic and vibrational structures of Au₂Al₂⁻ and Au₂Al₂ have been investigated using photoelectron spectroscopy (PES), high-resolution photoelectron imaging, and theoretical calculations. Photoelectron spectra taken at high photon energies with a magnetic-bottle apparatus reveal numerous detachment transitions and a large energy gap for the neutral Au₂Al₂. Vibrationally resolved PE spectra are obtained using high-resolution photoelectron imaging for the ground state detachment transition of Au₂Al₂⁻ at various photon energies (670.55−843.03 nm). An accurate electron affinity of 1.4438(8) eV is obtained for the Au₂Al₂ neutral cluster, as well as two vibrational frequencies at 57 ± 8 and 305 ± 13 cm⁻¹. Hot bands transitions yield two vibrational frequencies for Au₂Al₂⁻ at 57 ± 10 and 144 ± 12 cm⁻¹. The obtained vibrational and electronic structure information is compared with density functional calculations, unequivocally confirming that both Au₂Al₂⁻ and Au₂Al₂ possess C_2v tetrahedral structures