Identification of the Au–Au–H/D Bending Mode in Au2H and Au2D via Photoelectron Velocity Imaging Spectroscopy and Theoretical Calculations

Abstract We report the identification of the Au–Au–H/D bending mode in Au2H and Au2D using photoelectron velocity-map imaging spectroscopy combined with theoretical calculations. The adiabatic detachment energies are measured to be 3.452 ± 0.005 eV for Au2H– and 3.459 ± 0.005 eV for Au2D–. Two vibrational modes of the neutral species are resolved in the experimental spectra, namely, the Au–Au stretching mode at 150 ± 8 cm–1 for both isotopologues, and the Au–Au–H/D bending mode at 300 ± 10 cm–1 for Au2H and 214 ± 8 cm–1 for Au2D. These results unambiguously confirm a linear-to-bent geometry change upon photodetachment and highlight the power of combining isotope-edited photoelectron velocity-map imaging spectroscopy with theoretical calculations to resolve and assign low-frequency vibrational modes in metal hydride clusters.