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Abstract

The vibrational OH-stretch spectra of size-selected pure water (H₂O)₉ clusters, measured at two different temperatures, have been used to identify isomeric transitions. The broad, featureless high-temperature, liquid-like spectrum resembles that of water, while the structured low- temperature, solid- like spectrum differs appreciably from that of ice. Accompanying calculations suggest that the low-temperature spectra originate from two cube-like structures. The high temperature spectra appear to be above an isomeric transition to more open amorphous arrangements of fused three- to five- membered rings.