Sequential mechanism in H3+ formation dynamics on the ethanol dication

Abstract

Two- and three-body Coulomb explosion dynamics of isolated ethanol dications are studied via single-photon double-ionization with ultrafast extreme-ultraviolet pulses. The measured 3-body momentum correlations obtained via 3D coincidence imaging of the ionic products provide evidence for several concerted and sequential mechanisms: (1) a concerted 3-body breakup mechanism, with dominating channels such as CH₃⁺ + COH⁺ + H₂; (2) sequential dissociation in which the ejection of a low-kinetic-energy neutral OH precedes the Coulomb explosion of C₂H₅²⁺ → CH₃⁺ + CH₂⁺; and (3) a sequential 3-body breakup mechanism that dominates H₃⁺ formation from the ethanol dication via a mechanism that is different from the well-studied H₃⁺ formation in the 2-body Coulomb explosion of the methanol dication. Furthermore, we report surprising branching ratios of the competing C–O bond dissociation channels, resulting in H₃O⁺, H₂O⁺ and OH⁺ formation.