title: Near-infrared spectra of H2O under high pressure and high temperature: implications for a transition from proton tunneling to hopping states.
abstract: The nature of protons in ice VII up to 368°C and 16GPa was investigated with synchrotron near-infrared spectroscopy. The absorption band of the first OH stretching overtone mode divided into doublet peaks above 5GPa at room temperature, suggesting that proton tunneling occurs at the overtone level. As the temperature increased, the doublet peaks gradually reduced to a singlet. This result implies that thermally activated protons hop between the two potential minima along the oxygen-oxygen axis. A pressure-temperature diagram for the proton state was constructed from the changing band shape of the overtone mode.
authors: Geochemical Research Center, Graduate School of Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan. Electronic address: n-noguchi@hiroshima-u.ac.jp.
authors: Naoki
authors: N
authors: Noguchi
authors: Geochemical Research Center, Graduate School of Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors: Kazuki
authors: K
authors: Komatsu
authors: Geochemical Research Center, Graduate School of Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors: Ayako
authors: A
authors: Shinozaki
authors: Department of Geosciences, Graduate School of Science, Osaka City University, Sugimoto 3-3-138, Sumiyoshi-ku, Osaka 558-8585, Japan.
authors: Keiji
authors: K
authors: Shinoda
authors: Geochemical Research Center, Graduate School of Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors: Hiroyuki
authors: H
authors: Kagi
mesh_terms: D006358:Hot Temperature; D007053:Ice / Q000032:analysis; D011312:Pressure; D011522:Protons; D019265:Spectroscopy, Near-Infrared; D014867:Water / Q000737:chemistry*
chemical_list: D007053:Ice; D011522:Protons; D014867:Water
keywords: High pressure and high temperature; Ice; Near-infrared spectroscopy; Proton hopping; Proton tunneling