Ion-momentum imaging of dissociative attachment of electrons to molecules

Abstract

We present an overview of experiments and theory relevant to dissociative electron attachment studied by momentum imaging. We describe several key examples of characteristic transient anion dynamics in the form of small polyatomic electron-molecule systems. In each of these examples the socalled axial recoil approximation is found to break down due to correlation of the electronic and nuclear degrees of freedom of the transient anion. Guided by anion fragment momentum measurements and predictions of the electron scattering attachment probability in the molecular frame, we demonstrate that accurate predictions of the dissociation dynamics can be achieved without a detailed investigation of the surface topology of the relevant electronic states or the fragment trajectories on those surfaces.

Negative ion formation through dissociative electron attachment to the group IV tetrachlorides: Carbon tetrachloride, silicon tetrachloride and germanium tetrachloride

“…ref. [124] and refs. therein) would be well suited to remove all ambiguity with regards to these ion yields.…”

“…that at this time we can by no means exclude contributions from core-excited resonances associated with HOMO-LUMO transitions.Though the current picture of electron attachment and negative ion formation from these compounds is consistent and must be considered fairly complete, there are still ambiguities with regards to the assignment of individual contributions to the respective resonances. These ambiguities may be clarified through techniques such as velocity slice imaging and momentum imaging of the angular dependency of the DEA process, see for example refs [22,132]. and references therein.…”

Electron correlation effects in attosecond photoionization of CO2

“…In order to understand the dynamics captured in the time delay measurements shown in Fig. 1, we compare these data with predicted delays calculated using an implementation [38][39][40][41][42][43][44][45][46] of the complex Kohn variational method [47][48][49][50][51][52][53] for photoionization [54][55][56][57][58][59][60][61][62][63] and electron-molecule scattering [64][65][66][67][68][69][70][71][72][73]. The two-photon molecular photoionization time delays (τ PI ) are calculated in two different levels of approximation and then averaged over molecular orientation and outgoing electron direction, consistent with the measurement scheme used in the experiment (see the Appendix).…”

Breaking up is hard to do

“…Despite recent advances in electronic structure theory and computational techniques [6,7] the energies and lifetimes of the anion resonances are challenging to calculate. From the onset of an electron attachment reaction, electron-electron correlations can strongly couple the electronic and nuclear degrees of freedom, leading to a clear and immediate breakdown of the Born-Oppenheimer approximation.…”