Anharmonicities and Isotopic Effects in the Vibrational Spectra of X−·H2O, ·HDO, and ·D2O [X = Cl, Br, and I] Binary Complexes

Vibrational predissociation spectra of the argon-tagged halide monohydrates, X−·H2O·Ar (X = Cl, Br, or I), are recorded from ∼800 to 3800 cm−1 by monitoring the loss of the argon atom. We use this set of spectra to investigate how the spectral signatures of the hydrogen-bonding and large-amplitude h...

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Published in:The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 2010-01, Vol.114 (3), p.1556-1568
Main Authors: Horvath, Samantha, McCoy, Anne B, Elliott, Ben M, Weddle, Gary H, Roscioli, Joseph R, Johnson, Mark A
Format: Article
Language:English
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Summary:Vibrational predissociation spectra of the argon-tagged halide monohydrates, X−·H2O·Ar (X = Cl, Br, or I), are recorded from ∼800 to 3800 cm−1 by monitoring the loss of the argon atom. We use this set of spectra to investigate how the spectral signatures of the hydrogen-bonding and large-amplitude hindered rotations of the water molecule are affected by incremental substitution of the hydrogen atoms by deuterium. All six vibrational modes of the X−·H2O complexes are assigned through fundamental transitions, overtones, or combination bands. To complement the experimental study, harmonic and reduced-dimensional calculations of the vibrational spectra are performed based on the MP2/aug-cc-pVTZ level of theory and basis set. Comparison of these results with those from the converged six-dimensional calculations of Rheinecker and Bowman [ J. Chem. Phys. 2006, 125, 133206. ] show good agreement, with differences smaller than 30 cm−1. The simpler method has the advantage that it can be readily extended to the heavier halides and was found to accurately recover the wide range of behaviors displayed by this series, including the onset of tunneling between equivalent minima arising from the asymmetrical (single ionic hydrogen-bonded) equilibrium structures of the complexes.
ISSN:1089-5639
1520-5215
DOI:10.1021/jp9088782