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Abstract:
We have studied the structure of Ag microclusters using EXAFS. The measurements were performed over a wide range of cluster sizes at the National Synchrotron Light Source (NSLS), beam line X-18B. The clusters were prepared using the gas aggregation technique and isolated in solid argon at 4.2 K. A strong contraction of the interatomic distances was observed for Ag dimers and multimers. Clusters larger than a mean diameter of 20 Å show a small contraction of the nearest-neighbor distance and a structure consistent with an fcc lattice. By contrast, microclusters between 9 and 16 Å show a small nearest-neighbor expansion and a strong reduction or absence of higher-order shells in the EXAFS spectra. This suggests a different crystallographic structure for these Ag microclusters.
