Sequential mechanism in H 3 + 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 CH 3 + + COH + + H 2 ; (2) sequential dissociation in which the ejection of a low-kinetic-energy neutral OH precedes the Coulomb explosion of C 2 H 5 2+ → CH 3 + + CH 2 + ; and (3) a sequential 3-body breakup mechanism that dominates H 3 + formation from the ethanol dication via a mechanism that is different from the well-studied H 3 + 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 H 3 O + , H 2 O + and OH + formation.