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Persistent URL http://purl.org/net/epubs/work/52582
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Record Id 52582
Title Concerted proton tunelling in ordinary ice
Abstract We present incoherent neutron scattering measurements which reveal the presence of non-harmonic motions of protons in ordinary ice Ih down to 5K. A quasi-elastic scattering contribution, corresponding to a fast (~3 ps) and localized motion, has been observed. The corresponding dynamics is related to the hydrogen disorder since it is absent in the hydrogen-ordered phase, ice VIII. A main jump distance of 0.75 Angstrom is identified, i.e. close to the distance between the two possible proton sites along the oxygen-oxygen bond. The observed dynamics is non-Arhenius, has a large time rate 2.7 x1011 s-1, and affects only a small amount of the total number of hydrogen atoms in the crystal. A partial (20 %) deuteration of the sample hinders the observed dynamics. These observations strongly suggest the existence of concerted tunnelling of hydrogen atoms within the hexagonal rings of ice Ih, as predicted by Pauling [L. Pauling, J. Am. Chem Soc. 57, 2680, (1935)].
Organisation ISIS , ISIS-IRIS , STFC
Keywords RALSpace 2011-2012 , Physics , Chemistry
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Language English (EN)
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Journal Article Notiziario Neutroni 15, no. 1 (2010): 4-11. 2010