Dissociative electron attachments to ethanol and acetaldehyde: A combined experimental and simulation study

Dissociation dynamics of the temporary negative ions of ethanol and acetaldehyde formed by the low-energy electron attachments is investigated by using the anion velocity map imaging technique and ab initio molecular dynamics simulations. The momentum images of the dominant fragments O⁻/OH⁻ and CH₃⁻ are recorded, indicating the low kinetic energies of O⁻/OH⁻ for ethanol while the low and high kinetic energy distributions of O⁻ ions for acetaldehyde. The CH₃⁻ image for acetaldehyde also shows the low kinetic energy. With help of the dynamics simulations, the fragmentation processes are qualitatively clarified. A new cascade dissociation pathway to produce the slow O⁻ ion via the dehydrogenated intermediate, CH₃CHO⁻ (acetaldehyde anion), is proposed for the dissociative electron attachment to ethanol. After the electron attachment to acetaldehyde molecule, the slow CH₃⁻ is produced quickly in the two-body dissociation with the internal energy redistributions in different aspects before bond cleavages