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Dissociative electron attachment to CH2Cl2, CHCH3Cl2, and C(CH3)2Cl2.
Gordon A Gallup1, Ilya I Fabrikant
1Department of Physics and Astronomy, University of Nebraska, Lincoln, Nebraska 68588-0299, USA.
The Journal of Chemical Physics
|October 14, 2011
Summary
Theoretical studies reveal dissociative electron attachment (DEA) cross sections for chlorinated methanes. A large resonance width explains low DEA cross sections in CH2Cl2, confirming experiments but noting minor discrepancies.
Area of Science:
- Chemical Physics
- Theoretical Chemistry
- Electron-Molecule Interactions
Background:
- Dissociative electron attachment (DEA) is a fundamental process in chemistry and physics.
- Understanding DEA is crucial for fields like plasma chemistry and atmospheric science.
- Chlorinated methanes are relevant compounds with potential applications and environmental impact.
Purpose of the Study:
- To theoretically investigate the dissociative electron attachment (DEA) process for CH(2-n)(CH(3))(n)Cl(2) compounds (n=0, 1, 2).
- To elucidate the reasons for the unexpectedly low DEA cross section observed for CH(2)Cl(2).
- To compare theoretical findings with existing experimental data and identify areas for refinement.
Main Methods:
- Utilizing a combination of the finite-element discrete model and resonance R-matrix theory for theoretical calculations.
- Calculating DEA cross sections and resonance widths for the target molecules.
- Computing thermal rate coefficients to assess consistency with experimental measurements.
Main Results:
- The study confirms that a relatively large resonance width is responsible for the low DEA cross section in CH(2)Cl(2), aligning with experimental observations.
- Quantitative discrepancies between theoretical predictions and experimental results were identified.
- Calculated thermal rate coefficients indicate inconsistencies among different experimental measurement techniques (beam vs. swarm) for CH(2)Cl(2).
Conclusions:
- The theoretical model provides a plausible explanation for the observed DEA behavior in CH(2)Cl(2), emphasizing the sensitivity of cross sections to resonance width.
- Further refinement of theoretical parameters, particularly the resonance width, could improve agreement with experimental data.
- Inconsistencies in experimental measurements of rate coefficients highlight the need for continued experimental and theoretical investigation.
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