Making Sense of Coulomb Explosion Imaging

Area of Science:

• Physical Chemistry
• Chemical Physics
• Quantum Chemistry

Background:

• Coulomb explosion (CE) imaging is a powerful technique for studying molecular dynamics.
• Understanding fragmentation pathways in molecules like methanol is crucial for chemical physics.
• Nonadiabatic dynamics play a significant role in molecular dissociation.

Purpose of the Study:

• To identify novel mechanisms in Coulomb explosion-induced breakup of methanol.
• To elucidate the dynamics of two- and three-body fragmentation processes.
• To provide general concepts for analyzing time-resolved CE imaging of molecular systems.

Main Methods:

• Combined ab initio theoretical predictions with experimental measurements.
• Utilized weak ultrafast EUV pulses to initiate Coulomb explosion.
• Employed high-level quantum chemistry to simulate nonadiabatic molecular dynamics.
• Analyzed branching ratios, kinetic energy release, and momentum correlation spectra.

Main Results:

• Identified direct nonadiabatic CE causing CO bond-breaking.
• Discovered a long-range "inverse harpooning" mechanism producing H2+ + HCOH+.
• Observed transient proton migration leading to unique energy partitioning in three-body fragmentation.
• Characterized complex dynamics forming products like H2O+ and H3+.

Conclusions:

• The study reveals new, multifaceted mechanisms governing methanol's Coulomb explosion.
• These findings advance the understanding of molecular fragmentation and nonadiabatic dynamics.
• The identified concepts are applicable to future CE imaging studies of methanol and other molecules.