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Non-RRKM dynamics in the CH3O2 + NO reaction system
Philip J Stimac1, John R Barker
1Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, Michigan 48109-2143, USA.
The Journal of Physical Chemistry. A
|March 6, 2008
Summary
Quasi-classical trajectory calculations reveal that the decomposition of CH3OONO* deviates significantly from statistical Rice-Ramsperger-Kassel-Marcus (RRKM) theory, with anharmonicity playing a key role.
Area of Science:
- Chemical Kinetics
- Computational Chemistry
Background:
- The decomposition of CH3OONO* is a key reaction in atmospheric chemistry.
- Previous studies often assumed statistical Rice-Ramsperger-Kassel-Marcus (RRKM) rate theory for this reaction.
Purpose of the Study:
- To investigate the accuracy of statistical rate theory for the decomposition of CH3OONO*.
- To explore the role of anharmonicity in the reaction dynamics.
Main Methods:
- Quasi-classical trajectory (QCT) calculations were performed on a model potential energy surface (PES).
- The model PES accurately described the properties of CH3OONO isomers and included isomerization.
Main Results:
- QCT calculations showed strong deviations from RRKM theory for the CH3OONO* decomposition.
- Time-dependent rate constants and damped oscillations in decomposition rate were observed.
- Anharmonicity was found to reduce the rate constant by a factor of 10 compared to harmonic RRKM theory.
Conclusions:
- Statistical rate theory is inadequate for describing the CH3OONO* decomposition.
- Vibrational anharmonicity and non-RRKM effects likely explain discrepancies in previous organic nitrate yield studies.
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