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Abstract

In this work, a series of electron impact ionization studies on targets ranging from simple atoms to complex systems like clusters are summarized. The momenta of the ionization fragments are measured using a recoil-ion and electron momentum spectrometer called ‘Reaction Microscope’ (ReMi). The objectives of the thesis are two-fold. Firstly, two new target beam sources were constructed in order to enable, for the first time, kinematically complete (e,2e) experiments with the ReMi on substances which are solid at room temperature. As a result (e,2e) experiments were conducted on fundamental lithium and on a complex molecule, 1-Methyl,5-Nitroimidazole, which is among the potential radio-sensitizers under study for radiation therapy. The second part of the work is the study of intermolecular Coulombic decay (ICD) in the biologically relevant systems, thiophene dimers and pyridine D2O dimers. ICD initiated after ionization of the inner valence orbital 7a₁ is identified in thiophene dimers. A comparison of the obtained kinetic energy release (KER) distribution with ab initio molecular dynamics simulations indicates that a majority of the ionized dimers have a T-shaped conformational structure. In the hydrated pyridine dimer, it was found that ICD is initiated by the inner valence ionization of O 2s⁻¹ orbital of D2O. ICD initiated from the C 2s⁻¹ and N 2s⁻¹ orbitals of pyridine is assumed to be quenched by the open Auger and electron transfer mediated decay (ETMD) channels.