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UBC Theses and Dissertations

Photoionization studies of molecules by mass spectrometry Mak, Danny Shiu Hung


This thesis is an account of work on the photoionization of molecules using a beam of monochromatic light of considerably narrow band width. A mass spectrometer was used to differentiate the ions formed by photon impact, and to measure their intensity. At the beginning of the thesis, a brief account of the historical developments leading to the present work is described. A few existing methods for the determination of ionization potentials, and their advantages and limitations are pointed out. The major essential components of the instrument are itemised, and their special characteristics briefly discussed. Normal procedures and maintainance of the instrument, and simple calculations and the major sources of error are also included. Diagrams and tables are added in order to make the text easier to understand. The ionization and dissociation of six molecules were studied, namely, ammonia, nitrogen dioxide, nitromethane, nitric oxide, benzene and aniline. Their photoionization efficiency curves are interpreted, and the ionization potentials of the parent ions were determined. They are compared with the reported results from other sources, and the agreements and differences explained. A conclusion is included in the end of the thesis. The limitations of this instrument at the present stage are pointed out, and improvements are suggested. The choice of molecules for this -work is mentioned, and an outline for further work has also been included.

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