Ab initio molecular dynamics study on the electron capture processes of protonated methane (CH5+)

Area of Science:

• Chemical Dynamics
• Theoretical Chemistry
• Quantum Mechanics

Background:

• Protonated methane (CH5+) is a key intermediate in interstellar chemistry and plasma environments.
• Understanding electron capture reactions is crucial for modeling these environments.

Purpose of the Study:

• Investigate the electron capture dynamics of protonated methane (CH5+).
• Identify competing reaction channels and their dependencies on CH5+ geometry.
• Elucidate the mechanisms governing these dissociative electron recombination processes.

Main Methods:

• Direct ab initio molecular dynamics (MD) simulations.
• Examination of ground and low-lying CH5+ state structures (Cs, Cs, C2v symmetries).
• Inclusion of zero-point energy for initial structure generation in the Franck-Condon region.

Main Results:

• Two primary reaction channels were observed: CH5+ + e- -> CH4 + H (Channel I) and CH5+ + e- -> CH3 + H2 (Channel II).
• Channel II is exclusively observed from CH5+ geometries near the staggered Cs symmetry, where specific protons are electronically equivalent.
• Channel I results from a broader range of CH5+ initial structures.

Conclusions:

• The geometry of CH5+ significantly influences the outcome of electron capture reactions.
• Specific CH5+ structures favor the formation of H2, while others lead to H atom production.
• Theoretical insights into dissociative electron-ion recombination mechanisms are provided.