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Experimental Study of the Relationship Between Particle Size and Methane Sorption Capacity in Shale
Published on: August 2, 2018
Quasielastic electron scattering from methane, methane-d4, methane-d2, ethylene, and 2-methylpropane
G Cooper1, E Christensen, A P Hitchcock
1Department of Chemistry, McMaster University, Hamilton, Ontario L8S 4M1, Canada.
The Journal of Chemical Physics
|September 4, 2007
Summary
High momentum transfer electron scattering experiments reveal that the signal originates from classical electron Compton scattering, where electrons interact with individual atoms rather than the entire molecule.
Area of Science:
- Atomic and Molecular Physics
- Electron Scattering Spectroscopy
- Quantum Chemistry
Background:
- Recent studies reported quasielastic electron scattering from gaseous species at high momentum transfer.
- Initial findings for methane (CH4) and deuterated methane (CD4) were explained by independent atom electron Compton scattering.
- Alternative interpretations involving nondipole molecular vibrational excitation were proposed based on prior quantum mechanical calculations.
Purpose of the Study:
- To investigate the underlying mechanism of high momentum transfer quasielastic electron scattering from gaseous molecules.
- To differentiate between classical electron Compton scattering and nondipole molecular vibrational excitation models.
- To validate the independent atom model for complex molecules.
Main Methods:
- Experimental measurement of quasielastic electron scattering spectra for gaseous 2-methylpropane, ethylene, methane (CH4), CH2D2, and CD4.
- Utilized a momentum transfer of approximately 20 a.u. (2.25 keV impact energy, 100° scattering angle).
- Comparison of experimental spectra with predictions from the independent atom electron Compton scattering model.
Main Results:
- Experimental spectra exhibited a number of peaks corresponding to the different atomic isotopes within each molecule.
- The peak positions in the spectra were accurately predicted by the independent atom electron Compton scattering model.
- Relative intensities of the peaks showed reasonable agreement with the model's predictions.
Conclusions:
- The experimental results strongly support classical electron Compton scattering as the dominant mechanism for high momentum transfer quasielastic electron scattering.
- The independent atom model provides an accurate description of electron scattering from molecules at high momentum transfer.
- This study clarifies the interpretation of quasielastic electron scattering spectra from gaseous molecules.
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