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Abstract

α-Al₂O₃ surfaces are common in both engineered applications and the environment. Much prior work indicates that their properties, e.g., reactivity, polarity, and charge, change dramatically on interaction with water. Perhaps the simplest question that can be asked of α-Al₂O₃/water interaction is how a single water molecule interacts with the most stable α-Al₂O₃ surface: the α-Al₂O₃(0001). Over the last 15 years, a series of theoretical studies have found that water dissociatively adsorbs on α-Al₂O₃(0001) through two channels. However, to our knowledge no experimental evidence of these dissociation pathways has appeared. By combining sample preparation via supersonic molecular beam dosing, sample characterization via coherent, surface specific vibrational spectroscopy and electronic structure theory, we report the first experimental observation of reaction products of each, theoretically predicted, dissociation channel. These results thus overcome a 15 year old experiment/theory disconnect and make possible a variety of intriguing experiments that promise to provide significant new insights into water/Al₂O₃ and water/oxide interaction more generally.