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

Photoelectron spectra following photodetachment of the gold dicarbide anion, AuC2(-), 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 (2)A' ← (3)A' transition, involving states which we calculate to have bond angles ~147° but with a low barrier to linearity.