Studies of double- and triple-ionization energies of molecules

• Main Author: Jeffreys, N.
• Published: Swansea University 1999
• Subjects: 539.6
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637411

The two major objectives of these investigations were: i) to measure vertical double-ionization energies of molecules using a high-resolution double-charge-transfer spectrometer and, in order to interpret the experimental data, to calculate these energies using theoretical methods; ii) to develop a new experimental technique in order to measure vertical triple-ionization energies of molecules. The experimental techniques for the measurement of double- and triple-ionization energies are defined and discussed in Chapter 1 together with a review of double-charge-transfer studies to date. Two theoretical methods were applied to calculate double-ionization energies, these are discussed in Chapter 2. Double-ionization energies to ground states of dications were calculated using <I>ab initio</I> methods and double-ionization energies to ground and excited states were calculated using a semi-empirical multiple-scattering X-alpha method. Chapter 3 describes the principles of double-charge-transfer spectrometry, the double-charge-transfer experiment and the modified Finnigan 8230 mass spectrometer. The next three chapters are devoted to the studies of double ionization and a variety of molecular dications. Chapter 4 presents theoretical predictions of double-ionization energies of eleven fluorobenzene molecules and five alkyne molecules in order to interpret the experimental data of others. Chapter 5 presents high-resolution experimental studies of ethyne and ethene, and Chapter 6 presents a joint theoretical and experimental study of the double-ionization energies of six amine molecules. The final chapter in this thesis (Chapter 7) is devoted to the study of triple-ionization energies of molecules. A new experimental technique, given the name triple-charge-transfer spectrometry, was developed. The Finnigan 8230 spectrometer was adapted for triple-charge-transfer and the experiment was tested for effectiveness using krypton. Following favourable results for krypton, triple-charge-transfer studies of carbon disulphide, allene and ethene were presented. In order to interpret the spectra in terms of electronic transitions, the semi-empirical multiple-scattering X-alpha theoretical method was developed to predict triple-ionization energies.