Spectroscopic observation of gold-dicarbide: Photodetachment and velocity map imaging of the AuC2 anion

Photoelectron spectra following photodetachment of the gold dicarbide anion, AuC ₂^-, have been recorded using the velocity map imaging technique at several excitation wavelengths. The binding energy spectra show well-defined vibrational structure which, with the aid of computational calculations and Franck-Condon simulations, was assigned to a progression in the Au-C stretching mode, ν₃. The experimental data indicate that the features in the spectrum correspond to a ²A′ ← ³A′ transition, involving states which we calculate to have bond angles ∼147° but with a low barrier to linearity.