X-Ray Absorption Spectroscopy Of Small Copper-Oxide Cluster Ions For Analyses Of Cu Oxidation State And Ar Complexation: Cuoar+ And Cu2o2+

Small copper-oxide cluster cations, namely, CuOAr+ and Cu2O2+, are studied by mass spectrometry and X-ray absorption spectroscopy (XAS) to investigate the oxidation state of copper atoms. The XAS in Cu L-3-region revealed that the oxidation number of Cu is almost +2.1 and +2.3 for CuOAr+ and Cu2O2+, respectively, which are consistent with the natural charges obtained by quantum chemical calculation. It was also revealed that the binding energy of Ar to CuO+ is unexpectedly high to form CuOAr+ dominantly as a result of a significant amount of charge transfer to the Ar atom.