SPring-8, the large synchrotron radiation facility

The unique property of water, such as high boiling and melting point compared to molecules like non-metal hydride, or less density in solid form than in liquid form, are explained by an attractive force between water molecules, called 'hydrogen bond'. There are many proposed local structural models that describe the water network. Among them, a continuum model, where hydrogen bonds in water are distorted, broken and reformed continuously, but water itself is composed of a single component, or a mixture (micro-heterogeneity) model, where the network is considered as a mixture of various hydrogen bond configurations, are well known. However, the model that describes better the hydrogen bond property of liquid water, is still under debate.

Associate Professor Yoshihisa Harada from Institute for Solid State Physics and Synchrotron Radiation Research Organization, The University of Tokyo, and Dr. Takashi Tokushima, Engineer of RIKEN (President, Ryoji Noyori), in collabration with an international research team including scientists from Hiroshima University, Japan Synchrotron Radiation Research Institute (JASRI), University of Iceland, Stockholm University and SLAC National Accelarator Laboratory have succeeded in revealing validity of the mixture (micro-heterogeneity) model by selective observation of hydrogen-bond-broken water molecules and in detecting with high sensitivity the difference in the degree of hydrogen bond strength between light (normal) water and heavy water (in which both hydrogen atoms have been replaced with deuterium) using soft X-ray resonant inelastic scattering at University-of-Tokyo Synchrotron Radiation Outstation Beamline BL07LSU^*3 and RIKEN Coherent Soft X-ray Spectroscopy beamline BL17SU^*4 of SPring-8^*2.

The results of this research are expected to lead to the clarification of the role of water in various chemical and catalytic reactions as well as water in biological organisms where hydrogen bond plays an important role. The research result was published in Physical Review Letters (online published date: 8 Nov. 2013).

This work was supported by the Japan Society for the Promotion of Science (JSPS) through its Funding Program for World-Leading Innovative R&D on Science and Technology (FIRST) Program and by the Icelandic Research Fund.

Publication:
Title: "Selective Probing of the OH or OD Stretch Vibrations in Liquid Water using Resonant Inelastic Soft X-ray Scattering"
Authors: Yoshihisa Harada(1,2), Takashi Tokushima(3), Yuka Horikawa(1,3), Osamu Takahashi(4), Hideharu Niwa(1,2,5), Masaki Kobayashi(2,5), Masaharu Oshima(2,5), Yasunori Senba(6), Haruhiko Ohashi(6), Kjartan Thor Wikfeldt(7,8), Anders Nilsson(9,10), Lars G. M. Pettersson(10), and Shik Shin(1,2,3)
Affiliations: (1) Department of Physics, Nagoya University, (2) Japan Synchrotron Radiation Research Institute (JASRI), (3) Institute for Solid State Physics (ISSP), The University of Tokyo, (4) Department of Chemistry, Kobe University, (5) Institute for Materials Research (IMR), Tohoku University, (6) Department of Physics, Meiji University
Physical Review Letters 111 217801, published 18 November 2013
(1)Institute for Solid State Physics (ISSP), The University of Tokyo, (2)Synchrotron Radiation Research Organization, University of Tokyo, (3)RIKEN/SPring-8, (4)Department of Chemistry, Hiroshima University, (5)Department of Applied Chemistry, University of Tokyo, (6)JASRI/SPring-8, (7)Science Institute, University of Iceland, (8)NORDITA, AlbaNova University Center, (9)SUNCAT Center for Interface Science and Catalysis, SLAC National Accelerator Laboratory, (10)Department of Physics, AlbaNova University Center, Stockholm University
Physical Review Letters 111 193001, published 8 November 2013.