Hydrogen bond dynamics in aqueous NaBr solutions

Sungnam Park, M. D. Fayer

Research output: Contribution to journalArticle

246 Citations (Scopus)

Abstract

Hydrogen bond dynamics of water in NaBr solutions are studied by using ultrafast 2D IR vibrational echo spectroscopy and polarization-selective IR pump-probe experiments. The hydrogen bond structural dynamics are observed by measuring spectral diffusion of the OD stretching mode of dilute HOD in H 2O in a series of high concentration aqueous NaBr solutions with 2D IR vibrational echo spectroscopy. The time evolution of the 2D IR spectra yields frequency-frequency correlation functions, which permit quantitative comparisons of the influence of NaBr concentration on the hydrogen bond dynamics. The results show that the global rearrangement of the hydrogen bond structure, which is represented by the slowest component of the spectral diffusion, slows, and its time constant increases from 1.7 to 4.8 ps as the NaBr concentration increases from pure water to ≈6 M NaBr. Orientational relaxation is analyzed with a wobbling-in-a-cone model describing restricted orientational diffusion that is followed by complete orientational randomization described as jump reorientation. The slowest component of the orientational relaxation increases from 2.6 ps (pure water) to 6.7 ps (≈6 M NaBr). Vibrational population relaxation of the OD stretch also slows significantly as the NaBr concentration increases.

Original languageEnglish
Pages (from-to)16731-16738
Number of pages8
JournalProceedings of the National Academy of Sciences of the United States of America
Volume104
Issue number43
DOIs
Publication statusPublished - 2007 Oct 23

Keywords

  • Ultrafast 2D IR spectroscopy
  • Water dynamics in ionic solutions

ASJC Scopus subject areas

  • General

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