Sequential mechanism in H3+ formation dynamics on the ethanol dication

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.