Adsorption and Desorption of NO and NO2 Molecules on Gold Cluster Anions Observed by Thermal Desorption Spectrometry

The adsorption and thermal desorption of NO and NO2 molecules on gold cluster anions, Au-4(-), were experimentally observed using gas-phase thermal desorption spectrometry. Multiple collisions of NO molecules with Au-4(-) at 300 K generated Au-4(NO)(k)(-) (k = 1-3). The NO molecules desorbed from the clusters in a stepwise manner when the clusters were heated, and finally Au-4(-) was regenerated above 600 K. For NO2, Au4N2O4- was found to be thermally unstable. Hence, two NO2 molecules were sequentially released from Au4N3O6-, when Au4N3O6- was heated at 500-800 K, forming Au4NO2-. A gold oxide cluster, Au4O2-, was produced as a result of the decomposition of NO2 to NO and O on Au-4(-), and the NO molecules were released above 900 K.