Bridging the cluster-to-bulk divide: Electron attachment time-of-flight mass spectrometry reveals geometrical shell closings in (SF6)(n) clusters (n=2-550) - art. no. 183401

We report electron attachment time-of-flight mass spectra of SF6 clusters o ver a wide range of cluster sizes, revealing, a simple pattern of geometric al shell closings which persists from large clusters (n approximate to 500) to as small as perhaps n = 14. Quantitative structural properties of these nanocrystallites are derived. These observations, made possible by an extr aordinarily gentle ionization method and mass spectral analysis, suggest th at bulk crystalline packing may be important for much smaller molecular clu sters than previously observed, confirming theoretical predictions.