Selective probing of the OH or OD stretch vibration in liquid water using resonant inelastic soft-x-ray scattering

• Published in: Physical review letters Vol. 111; no. 19; p. 193001
• Main Authors: Harada, Yoshihisa, Tokushima, Takashi, Horikawa, Yuka, Takahashi, Osamu, Niwa, Hideharu, Kobayashi, Masaki, Oshima, Masaharu, Senba, Yasunori, Ohashi, Haruhiko, Wikfeldt, Kjartan Thor, Nilsson, Anders, Pettersson, Lars G M, Shin, Shik
• Format: Journal Article
• Language: English
• Published: United States 08-11-2013
• ISSN: 0031-9007; 1079-7114; 1079-7114
• DOI: 10.1103/physrevlett.111.193001

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.