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How do hydrogen bonds break in small alcohol oligomers?
1Department of Chemistry and Theoretical Chemistry Institute, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
The Journal of Physical Chemistry. A
|March 10, 2009
Summary
Ultrafast hydrogen bond breaking in alcohol oligomers occurs within 1 picosecond. This study models methanol dimer vibrational predissociation to explain the mechanism, revealing dependence on hydrogen bond strength.
Area of Science:
- Physical Chemistry
- Chemical Physics
- Spectroscopy
Background:
- Infrared pump-probe spectroscopy reveals ultrafast hydrogen bond (H-bond) breaking in alcohol oligomers.
- This process occurs on a time scale of 1 picosecond following OH stretch excitation.
Purpose of the Study:
- To elucidate the mechanism of H-bond breaking in alcohol oligomers.
- To investigate the vibrational predissociation of the hydrogen-bonded methanol dimer.
Main Methods:
- A four-dimensional model of the methanol dimer was constructed.
- The model included H-bond stretch, donor OH stretch, donor COH bend, and OH rotation.
- Predissociation rates were calculated using Fermi's golden rule and close coupling methods.
Main Results:
- Vibrational predissociation leads to products with highly excited OH rotations.
- Predissociation rates exhibit a strong dependence on hydrogen bond strength.
- A nonadiabatic curve crossing mechanism for predissociation was identified.
Conclusions:
- The study provides a framework for understanding solvent-assisted vibrational predissociation.
- The findings offer insights into the fundamental dynamics of H-bond breaking in molecular systems.
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