Ultrafast 2D IR anisotropy of water reveals reorientation during hydrogen-bond switching
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2DAnisotropy_revised.pdf
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Author(s)
Ramasesha, Krupa
Roberts, Sean Thomas
Nicodemus, Rebecca A.
Mandal, Aritra
Tokmakoff, Andrei
Date Issued
August 2011
Journal
Journal of Chemical Physics
Publisher
American Institute of Physics (AIP)
Citation
Ramasesha, Krupa et al. “Ultrafast 2D IR Anisotropy of Water Reveals Reorientation During Hydrogen-bond Switching.” The Journal of Chemical Physics 135.5 (2011): 054509. © 2011 American Institute of Physics
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Author's final manuscript
Abstract
Rearrangements of the hydrogen bond network of liquid water are believed to involve rapid and concerted hydrogen bond switching events, during which a hydrogen bond donor molecule undergoes large angle molecular reorientation as it exchanges hydrogen bonding partners. To test this picture of hydrogen bond dynamics, we have performed ultrafast 2D IR spectral anisotropy measurements on the OH stretching vibration of HOD in D[subscript 2]O to directly track the reorientation of water molecules as they change hydrogen bonding environments. Interpretation of the experimental data is assisted by modeling drawn from molecular dynamics simulations, and we quantify the degree of molecular rotation on changing local hydrogen bonding environment using restricted rotation models. From the inertial 2D anisotropy decay, we find that water molecules initiating from a strained configuration and relaxing to a stable configuration are characterized by a distribution of angles, with an average reorientation half-angle of 10°, implying an average reorientation for a full switch of ≥20°. These results provide evidence that water hydrogen bond network connectivity switches through concerted motions involving large angle molecular reorientation.
MIT Department
Massachusetts Institute of Technology. Department of Chemistry
Massachusetts Institute of Technology. Spectroscopy Laboratory
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DOI of Published Version
https://doi.org/10.1063/1.3623008
