Mid-infrared characterization of the NH <inf>4</inf><sup>+</sup> · (H <inf>2</inf> O)n clusters in the neighborhood of the n=20 "magic" number
- Diken, EG
- Hammer, NI
- Johnson, MA
- Christie, RA
- Jordan, KD
DOIAbstract
Vibrational predissociation spectra are reported for size-selected N H4+ middot; (H2 O)n clusters (n=5-22) in the 2500-3900 cm-1 region. We concentrate on the sharp free OH stretching bands to deduce the local H-bonding configurations of water molecules on the cluster surface. As in the spectra of the protonated water clusters, the free OH bands in N H4+ middot; (H2 O)n evolve from a quartet at small sizes (n<7), to a doublet around n=9, and then to a single peak at the n=20 magic number cluster, before the doublet re-emerges at larger sizes. This spectral simplification at the magic number cluster mirrors that found earlier in the H+ middot; (H2 O)n clusters. We characterize the likely structures at play for the n=19 and 20 clusters with e...
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