Structure of Au-4(0/-1) in the gas phase: A joint geometry relaxed ab initio calculations and vibrationally resolved photoelectron imaging investigation

We have combined photoelectron velocity-map imaging spectroscopy and high-level ab initio calculations to elucidate the geometries of Au-4(0/-1). Well-resolved ground-state electronic transition was observed in the photoelectron spectrum of Au-4 at 446 nm, leading to more accurate electron affinity and vibrational frequencies for the ground state of the neutral Au-4 . The pure and vibrationally resolved spectra provide definitive experimental evidence for the resolution of the ground-state gold tetramer in the gaseous phase, with the aid of the ab initio calculations and Franck-Condon simulations. The comprehensive comparisons between the experiment and theoretical calculations suggest that the Y-shaped structure is the global minimum for both the neutral and anionic Au-4. (C) 2013 AIP Publishing LLC