Dissociative electron attachment to polyatomic systems

In this dissertation, we have investigated molecular dissociation processes induced by electron collisions and addressed the inherent polyatomic effects involved. Dissociative electron attachment is known to be an important decay channel for resonant states formed in low-energy electron-molecule collisions. In analyzing these processes, the community has built an intuition based on studies of diatomics. The simple 1-D picture used in these studies appears to be inadequate for making correct predictions of the nuclear dynamics in the case of polyatomic systems where multiple degrees of freedom come into play.;Generally, dissociation processes involve distortions of the molecule's geometry thus lowering its point group symmetry. Symmetry breaking events are known to cause a split of degenerate states causing transformations of the potential energy surfaces' topology; thus, leading to intersurface interactions. It is therefore necessary to introduce the various effects of coupling between the states of the compound system {electron, molecule} into the study of polyatomic molecules dissociation dynamics.;Four polyatomic systems of astrophysical, biological and technological relevance have been treated by ab initio methods: acetylene (HCCH), hydrogen cyanide (HCN), hydrogen isocyanide (HNC) and cyano-acetylene (HCCCN). For each molecule, we constructed the complex potential energy surfaces using the complex Kohn variational method, performed nuclear dynamics computations within the multi-configuration time-dependent Hartree formalism and computed the dissociative electron attachment (DEA) cross sections. The dissociation dynamic behavior is discussed and the results are compared to available experimental data.