An investigation of the properties of ions, radicals and molecules by translational-energy-loss spectroscopy

This thesis employs double charge transfer spectroscopy (DCTS) to measure ionisation energies (primarily double ionisation energies) of a number of small molecules. DCTS is described in detail and the previous work in this field is reviewed. A discussion on the stability of molecular dications and the experimental techniques that have been used previously to measure the energies of dications is included. Many characteristics of the target molecule and the projectile ion affect the quality and the type of data obtained using DCTS. This subject is discussed and a number of ions are selected and examined for their potential as prospective projectile ions. The data available for measurement is affected by the cross-section for double electron capture reactions. An extension of the Landau-Zener theory is presented enabling the calculation of absolute cross-sections in double electron capture reactions. Calculated cross-sections are compared with measured cross-sections taken from the literature and with relative cross-sections measured in the present study. A 'reaction window' effect is observed in double electron capture reactions and its effect on double charge transfer spectra is discussed. Using a number of selected projectile ions, double ionisation energies of CO, CO₂, COS, CS₂ NH₃, CH₃Br, CCl₄, CCl₃F, CCl₂F₂ and C₂H₄ are measured and assigned, wherever possible, using relevant information from the literature. In addition, the electron-ion recombination energy of both SF₅₊ and SF₃₊ are determined as well as the electron affinity of each of the molecules SF₄, SF₂ and SF.