title: Selective probing of the OH or OD stretch vibration in liquid water using resonant inelastic soft-x-ray scattering.
abstract: High-resolution O 1s resonant inelastic x-ray scattering spectra of liquid H2O, D2O, and HDO, obtained by excitation near the preedge resonance show, in the elastic line region, well-separated multiple vibrational structures corresponding to the internal OH stretch vibration in the ground state of water. The energy of the first-order vibrational excitation is strongly blueshifted with respect to the main band in the infrared or Raman spectra of water, indicating that water molecules with a highly weakened or broken donating hydrogen bond are correlated with the preedge structure in the x-ray absorption spectrum. The vibrational profile of preedge excited HDO water is well fitted with 50%±20% greater OH-stretch contribution compared to OD, which strongly supports a preference for OH being the weakened or broken H-bond in agreement with the well-known picture that D2O makes stronger H-bonds than H2O. Accompanying path-integral molecular dynamics simulations show that this is particularly the case for strongly asymmetrically H-bonded molecules, i.e., those that are selected by preedge excitation.
authors.affiliation: Institute for Solid State Physics (ISSP), University of Tokyo, Kashiwanoha, Kashiwa, Chiba 277-8581, Japan and Synchrotron Radiation Research Organization, University of Tokyo, Sayo-cho, Sayo, Hyogo 679-5198, Japan.
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Harada
authors.forename: Takashi
authors.initials: T
authors.lastname: Tokushima
authors.forename: Yuka
authors.initials: Y
authors.lastname: Horikawa
authors.forename: Osamu
authors.initials: O
authors.lastname: Takahashi
authors.forename: Hideharu
authors.initials: H
authors.lastname: Niwa
authors.forename: Masaki
authors.initials: M
authors.lastname: Kobayashi
authors.forename: Masaharu
authors.initials: M
authors.lastname: Oshima
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Senba
authors.forename: Haruhiko
authors.initials: H
authors.lastname: Ohashi
authors.forename: Kjartan Thor
authors.initials: KT
authors.lastname: Wikfeldt
authors.forename: Anders
authors.initials: A
authors.lastname: Nilsson
authors.forename: Lars G M
authors.initials: LG
authors.lastname: Pettersson
authors.forename: Shik
authors.initials: S
authors.lastname: Shin