Multi-mass imaging in chemical reaction dynamics

Thesis

The work described in this thesis illustrates the application of multi-mass velocity-map imaging in the investigation of molecular fragmentation dynamics. Results from three experiments, focussing on three types of fragmentation processes, are reported. Firstly, a photofragmentation and photoionization study of niobium oxide (NbO) is presented. Analysis of the recorded velocity-map images yields refined values for the dissociation energies of NbO and NbO⁺, which are found to be 60,650±124 cm⁻¹ and 57,414 ± 124 cm⁻¹, respectively. In addition, the first steps towards the study of charged metal-ligand clusters are outlined using the example of the photofragmentation of the VCO₂⁺ complex.

In Chapter 3, the UV-induced photofragmentation dynamics of the CH₂BrI molecule are studied in a time-resolved UV-pump XUV-probe experiment. While the findings are largely consistent with previous studies on this system, evidence for charge transfer processes between the XUV ionized halogen photoproducts and neutral rotationally excited CH₂Br fragments are found.

Finally, Chapter 4 presents an experimental study of the dissociative electron ionization of CF₃I. Following the ionization step, dissociation of singly-charged parent ions proceeds via either the C-I bond or C-F bond breaking with very different dynamics. A mixture of `statistical' and `direct' bond breaking dynamics is observed, and can be rationalized by comparison with photoionization studies. Evidence for the fragmentation of doubly and triply charged ions is also found, with these processes apparently proceeding via a two-body Coulomb explosion followed by further fragmentation of the molecular product ion.

Authors: Kockert, H

• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: Multi-mass imaging; Ion imaging; Mass spectrometry; Laser spectroscopy; PImMS; Molecular beams; Velocity-map imaging; Electron ionization
• Subjects: Chemistry, Physical and theoretical