Volume 32, Issue 11, November 2006
Index of content:
32(2006); http://dx.doi.org/10.1063/1.2389018View Description Hide Description
We have studied fluorescence spectra of small and clusters embedded in large host clusters, excited with SR excitation in the VUV spectral region above the atomic limit. The IR emission bands due to ionic chromophores as well as UV and visible bands due to desorbed excimer molecules have been observed. The triatomic excimer emission has only been observed under low-energy excitation close to the lowest xenon exciton absorption band. A competition between ionic and charge-transferreaction channels is followed as a function of the cluster sizes and .
32(2006); http://dx.doi.org/10.1063/1.2389019View Description Hide Description
Electron or photon irradiation of adsorbed on the surface of rare gas solids induces the desorption of protonated water clusters, . The yield and the size distribution of cluster ions depend on the coverage, the deposition temperature of the water, and the thickness of the rare gas film. These results indicate that the ions originate from the isolated water clusters, and the most important factor determining the size distribution of desorbed is the sizes of water islands on the rare gas solid. The measurement of kinetic energy distributions indicated that the desorbing energy of clusters depend on the rare gas species of the substrates and the cluster size. It is suggested that the desorption is due to Coulomb repulsion between the ionic water cluster and the rare gas ion.
32(2006); http://dx.doi.org/10.1063/1.2389021View Description Hide Description
The polymerization of acetylene was studied by thermal programmed reaction on model catalysts consisting of size-selected Ag, Rh, and Pd atoms and clusters on well-characterized MgO(111) thin films. In a single-pass heating cycle experiment, benzene, butadiene, and butane were catalyzed with different selectivities as function of cluster size: palladium and rhodium atoms selectively produce benzene, and the highest selectivity for butadiene is observed for , whereas reveals the highest selectivity for butane. Ag atoms are inert. These results provide an atom-by-atom observation of the selectivity of small cluster catalysts.