Anomalous proton dynamics in ice at low temperatures

We present incoherent quasielastic neutron scattering measurements on ice Ih (ordinary ice) and Ic (cubic ice) which show the existence of nonharmonic motion of hydrogen at low temperatures, down to 5 K. We show that this dynamics is localized, nonvibrational, and related to the hydrogen disorder si...

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Bibliographic Details
Published in:Physical review letters 2009-10, Vol.103 (16), p.165901-165901, Article 165901
Main Authors: Bove, L E, Klotz, S, Paciaroni, A, Sacchetti, F
Format: Article
Language:English
Subjects:
BARYON REACTIONS
BARYONS
CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS
Condensed Matter
CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
CRYSTALS
DIRECT REACTIONS
ELEMENTARY PARTICLES
ELEMENTS
FERMIONS
HADRON REACTIONS
HADRONS
HYDROGEN
ICE
MATERIALS SCIENCE
NEUTRON REACTIONS
NONMETALS
NUCLEAR REACTIONS
NUCLEON REACTIONS
NUCLEONS
Other
OXYGEN
Physics
PROTONS
QUASI-ELASTIC SCATTERING
QUASI-FREE REACTIONS
SCATTERING
TUNNEL EFFECT
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Summary:We present incoherent quasielastic neutron scattering measurements on ice Ih (ordinary ice) and Ic (cubic ice) which show the existence of nonharmonic motion of hydrogen at low temperatures, down to 5 K. We show that this dynamics is localized, nonvibrational, and related to the hydrogen disorder since it is absent in ordered ice VIII. A main jump distance of 0.75 A is identified, hence close to the distance between the two possible proton sites along the oxygen-oxygen bond. The dynamics is non-Arrhenius, has a large time rate of 2.7x10(11) s-1, and affects only a few percent of the total number of hydrogen atoms in the crystal. These results give evidence for the existence of concerted proton tunneling in these ice phases.
ISSN:0031-9007
1079-7114
DOI:10.1103/PhysRevLett.103.165901