Dissociative electron attachment to methane probed using velocity slice imaging

Origin of resonant character in the electron impact two-body neutral-fragmentation of methane

The observation of peaks in the threshold region of two-body neutral fragmentation of methane molecule, i.e.,  CH 4   ->  CH 3 + H, by low energy electron (LEE) impact has been an enigma. The prevailing explanation that this resonant behavior is due to excitation energy transfer is unsatisfactory since this process is not expected to show peaks in the cross-sections unless there is the involvement of electron-molecule resonances. Our first-principles calculations now reveal that the observed peaks could be explained as due to the formation of negative ion resonances, which dominantly dissociate into two neutral fragments and a free-electron. This case of methane is a pointer to the possibility that such reactions contribute significantly to neutral radical production from molecules by LEE impact in comparison to dissociative electron attachment, and in general could play a significant role in electron-based chemical control.

Signatures of bond formation and bond scission dynamics in dissociative electron attachment to methane

We show that a single T₂ resonance can explain the 10 eV dissociative electron attachment peak in methane.

Dissociative electron attachment studies on acetone

Dissociative electron attachment (DEA) to acetone is studied in terms of the absolute cross section for various fragment channels in the electron energy range of 0-20 eV. H(-) is found to be the most dominant fragment followed by O(-) and OH(-) with only one resonance peak between 8 and 9 eV. The DEA dynamics is studied by measuring the angular distribution and kinetic energy distribution of fragment anions using Velocity Slice Imaging technique. The kinetic energy and angular distribution of H(-) and O(-) fragments suggest a many body break-up for the lone resonance observed. The ab initio calculations show that electron is captured in the multi-centered anti-bonding molecular orbital which would lead to a many body break-up of the resonance.

Quantum superposition of target and product states in reactive electron scattering from CF4 revealed through velocity slice imaging

Exploiting the technique of velocity slice imaging, we have performed a detailed study of reactive electron scattering with CF4. We have measured the electron impact energy dependence of both the angular and kinetic energy distributions of the channels yielding F- and CF3(-) anions. These data provide an unprecedented insight into the quantum superposition of the target state and product channels, respectively, of Td and C3v symmetry, and shed new light on the dissociation dynamics.