Gently Probing Bulk-like Clusters

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Science  26 Oct 2001:
Vol. 294, Issue 5543, pp. 749
DOI: 10.1126/science.294.5543.749c

Small clusters of atoms or molecules may differ in structure from the equivalent bulk material, with the size at which the transition to bulk structure occurs depending on the material. Theoretical predictions suggest that neutral weakly bound molecules may form the bulk structure at small cluster numbers, but experimental verification of this has been difficult. Molecular beam electron diffraction provides structural information about large clusters, but resolution deteriorates for clusters with fewer than several hundred molecules. Electron impact mass spectrometry can lead to extensive fragmentation, and the products tend to reflect the properties of ionic clusters and molecules more than those of neutral ones.

To overcome these problems, Ingólfsson and Wodtke have studied SF6 clusters with the gentle approach of electron attachment mass spectrometry. The authors conclude that bulk structures are indeed formed by clusters smaller than 50 molecules, confirming theoretical predictions.—JU

Phys. Rev. Lett. 10.1103/PhysRevLett.87.183401.

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