%0 Journal Article
%@ 0036-8075
%A Shin, JW
%A Hammer, NI
%A Diken, EG
%A Johnson, MA
%A Walters, RS
%A Jaeger, TD
%A Duncan, MA
%A Christie, RA
%A Jordan, KD
%D 2004
%F pittir:18123
%J Science
%N 5674
%P 1137 - 1140
%T Infrared signature of structures associated with the H<sup>+</sup>(H <inf>2</inf>O)<inf>n</inf> (n = 6 to 27) clusters
%U http://d-scholarship-dev.library.pitt.edu/18123/
%V 304
%X 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.