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Fragmentation mechanisms for methane induced by 55 eV, 75 eV, and 100 eV electron impact
1Applied Ion Beam Physics Laboratory, Fudan University, Key Laboratory of the Ministry of Education, Shanghai 200433, China.
The Journal of Chemical Physics
|April 5, 2014
Summary
Researchers investigated the fragmentation of methane dications (CH4 2+) using electron impact. They identified distinct reaction pathways, including concerted and stepwise mechanisms, for the breakup of these doubly charged molecular ions.
Area of Science:
- Atomic and Molecular Physics
- Chemical Physics
- Physical Chemistry
Background:
- Methane dications (CH4 2+) are unstable and undergo fragmentation.
- Understanding fragmentation mechanisms is crucial for molecular dynamics studies.
Purpose of the Study:
- To investigate the fragmentation pathways of CH4 2+ dications.
- To differentiate between single and multiple-step fragmentation processes.
- To analyze the kinetic energy release in different fragmentation channels.
Main Methods:
- Cold Target Recoil-Ion Momentum Spectroscopy (COLTRIMS) was employed.
- Electron impact ionization at 55 eV, 75 eV, and 100 eV was used.
- Momentum measurements of recoil ions were used to deduce neutral particle momentum and kinetic energy release.
Main Results:
- The fragmentation of CH4 2+ was observed through various mechanisms.
- Three distinct reaction channels were identified for the formation of CH2 (+), H(+), and H.
- Both synchronous concerted and two-step reaction pathways were observed.
Conclusions:
- The study successfully identified and differentiated complex fragmentation mechanisms of CH4 2+ dications.
- The kinetic energy release distributions provide insights into the dynamics of dissociation.
- Ion-ion coincidence spectra analysis, including peak slopes, aids in elucidating fragmentation dynamics.
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