Thesis (Ph. D.)--University of Wisconsin--Madison, 1978. / Typescript. Vita. Bibliography: leaves 249-251.

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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. / Science, Faculty of / Chemistry, Department of / Graduate

A series of isomeric tricyclic [3.2.1.0²̕⁴] oct-8—[symbols omitted] derivatives have been studied by photoionization mass spectrometry and the low resolution mass spectra of the compounds obtained. The observed differences in the relative intensities in the spectra of the isomers are explained on the basis of the geometry of the tricyclic system. The major fragments of the low resolution spectra were 'mass measured' to determine their elemental composition and, from the information obtained, possible fragmentation pathways are postulated. In addition, the ionization potential of all isomers was determined by electron impact. / Science, Faculty of / Chemistry, Department of / Graduate

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The research for this dissertation project began with the goal to construct a snapshot imaging spectropolarimeter forthe visible spectrum. The instrument integrates a channeled spectropolarimeter (CHSP) into a computed tomographicimaging spectrometer (CTIS), the result being an instrument that measures the complete spatially- andspectrally-resolved Stokes vectors of a scene. It is not the first of its kind, since a similar instrument has beenbuilt before for use in the short-wave infrared. However, that instrument encountered severe difficulties due tolimitations of available hardware. Visible spectrum work generally enjoys the best instrumentation available, providingan ideal place to attempt a proof-of-concept demonstration.The main body of the research is focused on finding ways to improve the CTIS measurement technique, especially in waysallowing it to integrate with channeled spectropolarimetry. The first effort is a careful analysis and reworking of thecalibration procedure for the instrument, followed by a survey and comparison of ideas for alternative CTIS designs.The second effort makes use of the new calibration approach to develop an alternative way of thinking about CTISreconstructions based on the geometry and physics of the instrument rather than on abstract matrix mathematics. Thisopens up ways to improve their accuracy and to achieve reconstructions at a much higher speed.Experimental results from the instrument illustrate the improvements obtained from using the new methods, showing itscurrent capabilities and limitations.

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<p dir="ltr">In mass spectrometry, analyte molecules are ionized by various mechanisms, such that they can be manipulated by electric and magnetic fields. By performing such manipulations, the mass to charge (<i>m/z</i>) ratio of the analyte molecules can be measured. Many methods for ion manipulation that allow for such <i>m/z </i>determination have been developed in the form of different mass analyzers. These include but are not limited to magnetic/electric sector instruments, time-of-flight (TOF) mass analyzers, 3D quadrupole ion traps, quadrupole mass filters, linear quadrupole ion traps (LITs), Fourier-transform ion cyclotron resonance (FT-ICR) instruments, Orbitrap mass analyzers, and electrostatic linear ion traps (ELITs). Each of these mass analyzers has unique advantages and disadvantages resulting from its specific mechanism of operation, allowing each of these to find a niche in mass spectrometry applications. The ELIT is a mass analyzer composed of two opposing ion mirrors, which cause trapped high energy ions to oscillate along a linear axial trajectory. The oscillation period of ions in the ELIT is dependent on injection energy, the potential energy and electrode geometry of the ELIT, and the ion <i>m/z</i> ratio. As such, mass spectra can be measured by measuring the frequency of ion packets in the ELIT in Fourier-transform (FT) operation mode, or by or by allowing ions to separate spatially in an <i>m/z </i>dependent manner before detection via a microchannel plate (MCP) in multiple-reflection time-of-flight (MR-TOF) mode of operation. The ability to perform two orthogonal mass analysis techniques in a single mass analyzer is one key advantage of the ELIT. Both FT-MS, and MR-TOF mode of operation are high-resolution techniques, making the ELIT unique in its excellent performance characteristics despite low complexity and manufacturing cost. Additionally, the ELIT can be used to perform high-resolution ion isolations, which makes it especially attractive for tandem-MS.</p><p dir="ltr">In chapter 1, the operating principles for MR-TOF and FT-MS modes of operation in an ELIT are discussed. In chapter 2 and 3, the performance, limitations, and applications of the mirror-switching isolation technique in the ELIT are discussed. Given the high-resolution performance of the ELIT for both mass analysis and ion isolation, it is clear that the ELIT has great potential for tandem-MS applications which require high-resolution in either the precursor selection, mass analysis step, or both. In chapters 4, 5, and 6, the implementation and development of infrared multi-photon dissociation, and surface-induced dissociation techniques in the ELIT are discussed, and it is shown that the ELIT can be used to as a standalone tandem mass spectrometer. While not performed on the ELIT instrument, the charge-based valet parking technique discussed in chapter 7 applies to tandem-MS as a whole, as it is shown to improve fragment yield in ETD. Finally, in chapter 8, the future directions of development for the ELIT mass analyzer are discussed.</p>

<p>High-resolution mass spectrometry (MS) and tandem mass spectrometry (MS/MS) are powerful tools for the characterization of the molecular structures of components of both simple and complex mixtures. MS and MS/MS have played key roles in many fields, including proteomics, metabolomics, and petroleomics. This thesis focuses on the development of tandem mass spectrometric methods for the structural characterization of asphaltenes and small isomeric molecules. In addition, this thesis also presents a method to address a sampling bias in asphaltene analysis. </p>