High resolution photoelectron imaging of Au2(-).

We report high resolution photoelectron spectra of Au2(-) using a newly built photoelectron imaging apparatus. Vibrationally resolved photoelectron images are obtained for the ground state detachment transition of Au2(-) at various photon energies (442.80-670.18 nm) at a resolution of 3 cm(-1) for low energy electrons. Franck-Condon simulations yield the vibrational temperature of Au2(-) and the high resolution data yield accurate spectroscopic constants for the ground states of Au2 and Au2(-). The electron affinity of Au2 is measured to be 1.9393 ± 0.0006 eV. A more precise value for the Au2(-) dissociation energy is also obtained as 1.937 ± 0.005 eV.