Infrared signature of structures associated with the H+(H2O)n (n = 6 to 27) clusters.

Shin, J-W; Hammer, N I; Diken, E G; Johnson, M A; Walters, R S; Jaeger, T D; Duncan, M A; Christie, R A et al. · Science · 2004

basic_science · Level V

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Abstract

We report the OH stretching vibrational spectra of size-selected H+(H2O)n clusters through the region of the pronounced "magic number" at n = 21 in the cluster distribution. Sharp features are observed in the spectra and assigned to excitation of the dangling OH groups throughout the size range 6 </= n </= 27. A multiplet of such bands appears at small cluster sizes. This pattern simplifies to a doublet at n = 11, with the doublet persisting up to n = 20, but then collapsing to a single line in the n = 21 and n = 22 clusters and reemerging at n = 23. This spectral simplification provides direct evidence that, for the magic number cluster, all the dangling OH groups arise from water molecules in similar binding sites.