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REPRESENTATIVE ACHIEVEMENTS
■ Icosahedral Clusters Successfully Stabilized
It was demonstrated that the structure of metal cluster is entirely different from that of crystal consisting of infinitely large number of atoms by using gold cluster. It was also found that cluster of gold-copper alloy in highly symmetric icosahedral structures could be stabilized up to a very large size. (See the figure at the right.)
■ Chemical Reaction Properties of Metal Cluster Dependent on Size
The properties of clusters vary extensively depending on their size. The graph at right shows how the reaction between cluster of transition metal (niobium) and hydrogen is affected by size. A small change in size causes the rate constant as much as 10,000 times. In this way, it is possible that cluster of particular size works as a high performance catalyst.
■ Observation of Microscopic Structure of Water, Hydration of Ion
In order to observe clusters formed around ions in water, an electro-spray ion cluster analyzer in which ion clusters are isolated out of solution and led to a mass spectrometer (Figure a). Fig. b shows the mass spectrum of clusters prepared from aqueous solution of nitric acid ob served by this method. It is evident that protons (H+) dissociated from nitric acid molecule (HNO3) is dispersed by hopping through water clusters. This study enabled approach to liquid phase at molecular level.
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