O₂ photodesorption from AuO ⁻₂ and Au₂O ⁻₂

Abstract

Using time-resolved photoelectron spectroscopy, the decay channels of AuO ⁻₂ and Au₂O ⁻₂ following photoexcitation with 3.1-eV photons have been studied. For AuO ⁻₂ , a state with a rather long lifetime of 30 ps has been identified. Its decay path could not be determined but photodesorption can be excluded. For Au₂O ⁻₂ , the spectra indicate O₂ desorption after 3.1-eV photoexcitation on a time scale of 1 ps. While comparing these results on Au _n O ⁻₂ with analogous data on Ag _n O ⁻₂ clusters, a discernible pattern emerges: for dissociatively bound O₂(AuO ⁻₂ , Ag₃O ⁻₂ ), there are long-living excited states which do not decay by oxygen desorption, while for molecular chemisorption (Au₂O ⁻₂ , Ag₂O ⁻₂ , Ag₄O ⁻₂ , Ag₈O ⁻₂ ), the 3.1-eV photoexcitation triggers fast O₂ desorption with a high quantum yield.