High resolution X-ray emission spectroscopy of liquid water: The observation of two structural motifs
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The structure of liquid water is presently under intense debate. We summarize the historical development of the present description of water and the controversy surrounding the X-ray absorption spectroscopy (XAS) study of Wernet et al. [Ph. Wernet et al., Science 304 (2004) 995]. In order to provide further insight into the connection between X-ray spectroscopy and the structure of the hydrogen bonding network, we report new data comprising high resolution oxygen K-edge X-ray emission spectra (XES) of liquid water. We observe two distinct narrow lone-pair derived peaks, assigned, respectively, to tetrahedral and strongly distorted hydrogen-bonded species; the assignment is based on comparison with ice and gas phase spectra, temperature dependent measurements, excitation energy dependence and theoretical simulations. We estimate a 2:1 ratio between distorted and tetrahedral species at room temperature and discuss what this implies in connection to the previous XAS study and in terms of liquid water structure.
|Number of pages||14|
|Journal||Chemical Physics Letters|
|Publication status||Published - 2008 Jul 30|