Hydrogen migration in triply charged acetylene.

Area of Science:

• Chemical Physics
• Molecular Dynamics
• Atomic and Molecular Collisions

Background:

• Investigating the behavior of highly charged molecular ions provides insights into fundamental chemical processes.
• Acetylene (C2H2) is a fundamental hydrocarbon molecule, and its behavior under extreme ionization conditions is not fully understood.

Purpose of the Study:

• To provide direct experimental evidence for hydrogen migration in triply charged acetylene ions (C2H2 3+).
• To elucidate the dissociation dynamics and identify the different pathways involved in the breakup of C2H2 3+.

Main Methods:

• Utilizing recoil ion momentum spectroscopy to precisely measure the momenta of fragment ions.
• Generating triply charged acetylene ions through collisions with slow, highly charged Xenon ions (Xe9+).

Main Results:

• Observed and confirmed the counter-intuitive phenomenon of hydrogen atom migration in C2H2 3+.
• Identified and separated three distinct dissociation pathways: concerted breakup (acetylene and vinylidene configurations) and sequential breakup via a [C2H]2+ intermediate.
• Quantified the branching ratios for each of the identified dissociation pathways.

Conclusions:

• The study provides the first direct experimental evidence of hydrogen migration in triply charged acetylene.
• The identified dissociation pathways and their branching ratios offer a comprehensive understanding of the fragmentation dynamics of C2H2 3+.
• These findings contribute to the broader understanding of molecular ion fragmentation and hydrogen atom roaming in complex systems.