Formation of H3O+ in the Ionization and Fragmentation of Ethanol Induced by Electron Beam Irradiation

The single ionization and dissociation of ethanol molecules induced by low-energy electrons ( E 0 = 90 eV ) are investigated using multiparticle coincident momentum spectroscopy. By detecting two outgoing electrons ( e 1 and e 2 ) and one fragment ion in coincidence, we obtain the energy deposition ( E 0 − E 1 − E 2 ) during electron ionization of the molecule, i.e., the binding energy spectra, for production of the different ionic fragments C2H5OH+, C2H4OH+, COH+, and H3O+. These data allow us to study the ionization channels for different ionic products. In particular, we focus on H3O+ as a product of double hydrogen migration. It is found that this channel mainly originates from the ionization of outer-valance orbitals (3a ″ ,10a ′ , 2a ″ , 9a ′ , 8a ′ , 1a ″ , and 7a ′ ). Additionally, there are minor contributions from the inner-valence orbitals such as 6a ′ , 5a ′ , and 4a ′ . Quantum chemistry calculations show two fragmentation pathways: concerted and sequential processes for formation of H3O+.