How O-Binding Affects Structural Evolution of Medium Even-Sized Gold Clusters Au ( = 20-34).

We report the first joint anion photoelectron spectroscopy and theoretical study on how O-binding affects the structures of medium even-sized gold clusters, Au ( = 20-34), a special size region that entails a variety of distinct structures. Under the temperature conditions in the current photoelectron spectroscopy experiment, O-bound gold clusters were observed only for = 22-24 and 34. Nevertheless, O binding with the clusters in the size range of = 20-34 can be still predicted based on the obtained global-minimum structures. Consequently, a series of structural transitions, from the pyramidal to fused-planar to core-shell structures, are either identified or predicted for the AuO clusters, where the O-binding is in either or fashion. The identified global-minimum structures of AuO ( = 20-34) also allow us to gain improved understanding of why the clusters Au ( = 26-32) are less reactive with O in comparison to others.