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Absolute total electron impact ionization cross-sections for many-atom organic and halocarbon species
James N Bull1, Peter W Harland, Claire Vallance
1Chemistry Research Laboratory, Department of Chemistry, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom.
The Journal of Physical Chemistry. A
|December 7, 2011
Summary
Estimating electron impact ionization cross-sections for molecules is challenging. This study shows three models accurately predict these values for polyatomic organic and halocarbon species, aiding future research.
Area of Science:
- Atomic and Molecular Physics
- Chemical Physics
- Physical Chemistry
Background:
- Experimental determination of absolute total electron impact ionization cross-sections for polyatomic molecules is historically difficult and limited.
- A need exists for reliable methods to predict these cross-sections for a wider range of species.
Purpose of the Study:
- To review and assess the performance of three models for estimating maximum electron impact ionization cross-sections.
- To compare model predictions with experimental data for a diverse set of polyatomic organic and halocarbon species.
Main Methods:
- Evaluation of an empirical correlation between ionization cross-section and molecular polarizability.
- Assessment of the binary encounter Bethe (BEB) model.
- Analysis of the functional group additivity model.
- Experimental measurements using a single instrument for a dataset of ~65 species.
Main Results:
- All three models demonstrated excellent agreement with experimental data.
- High-quality calculated electronic structure parameters were crucial for the empirical correlation and BEB model accuracy.
- The models allow prediction of total electron-impact ionization cross-sections with at least 7% precision.
Conclusions:
- The reviewed models are effective for predicting electron impact ionization cross-sections for uncharacterized polyatomic molecules.
- This work provides a valuable dataset and validated methods for researchers in related fields.
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