Desorption Energy of Oxygen Molecule from Anionic Gold Oxide Clusters, AunO₂–, Using Thermal Desorption Spectrometry

We determined the desorption energies of O 2 molecules from Au n O 2 – ( n = 2, 4, 6, 8, 10, 12, and 14) by gas phase thermal desorption spectrometry. Cluster anions, Au n O 2 –, prepared in the gas phase were heated inside a temperature-controlled copper tube. Formation of Au n – from the desorption of O 2 was observed as a function of temperature. Temperature dependence of the intensities of Au n O 2 – and Au n – was analyzed using the Arrhenius equation, estimating the desorption energy of O 2 from Au n O 2 – . Considering the geometrical structure of Au n O 2 –, the desorption energy must be the same as or slightly higher than the binding energy of O 2 to Au n –, because the desorption of O 2 proceeds by a simple bond cleavage of Au n – –O 2, without significant rearrangement of atoms in the cluster. The collision-induced dissociation experiments show that the desorption energy was nearly equal to or slightly lower than the threshold energy for n = 2, 4, and 6.