Sequential mechanism in H₃⁺ formation dynamics on the ethanol dication.

Area of Science:

• Physical Chemistry
• Atomic and Molecular Physics
• Ultrafast Spectroscopy

Background:

• Understanding molecular dissociation dynamics is crucial for fields like materials science and astrochemistry.
• Ethanol dications are relevant molecular systems for studying Coulomb explosion mechanisms.
• Previous studies have focused on simpler dications, leaving complex dynamics of larger molecules less explored.

Purpose of the Study:

• To investigate the two- and three-body Coulomb explosion dynamics of isolated ethanol dications.
• To elucidate the concerted and sequential dissociation mechanisms following single-photon double-ionization.
• To characterize the formation pathways of various ionic fragments, including H3+.

Main Methods:

• Single-photon double-ionization of ethanol molecules using ultrafast extreme-ultraviolet (XUV) pulses.
• Three-dimensional (3D) coincidence imaging of ionic products to measure momentum correlations.
• Analysis of fragmentation patterns to identify dissociation mechanisms and branching ratios.

Main Results:

• Evidence for both concerted and sequential three-body breakup mechanisms in ethanol dications.
• Dominant concerted channel identified as CH3+ + COH+ + H2.
• Observation of sequential dissociation involving neutral OH ejection and Coulomb explosion of C2H52+, as well as a distinct sequential pathway for H3+ formation.

Conclusions:

• Ethanol dication Coulomb explosion exhibits complex dynamics with multiple competing pathways.
• The H3+ formation mechanism differs significantly from that observed in smaller molecules like methanol.
• Surprising branching ratios were observed for C-O bond dissociation channels, leading to H3O+, H2O+, and OH+.