Mechanisms and Kinetics of Electron Impact Ionization of Atoms, Molecules, and Clusters

Abstract

Whereas inelastic interaction of free electrons with gas phase atoms or molecules results in changes of the electronic (ionization) and/or nuclear motion (vibrational and rotational excitation), respectively, interaction of electrons with atomic or molecular clusters (van der Waals cluster) may comprise multiple inelastic electron collisions and may involve subsequent intra- and intermolecular reactions within the cluster. These sequence of events leads to the production of excited cluster ions (different in composition and stoichiometry from the neutral precursors) involving the deposition of excess energy into various degrees of freedom. Energy and charge exchange between different sites in the cluster may in turn cause additional spontaneous reactions not present in gas phase atoms and molecules. These reactions on time scales ranging from a few vibrational oscillations up to the millisecond time regime will strongly contribute to the fragmentation pattern observed.