Mass spectrometry imaging (MSI) is a powerful tool that provides mass-specific surface images with micron or sub-micron spatial resolutions. In a microscope MSI experiment, large sample surfaces are illuminated with a defocused laser or primary ion beam, enabling all surface molecules to be desorbed and ionised simultaneously before being electrostatically projected onto a position-sensitive imaging detector at the end of a time-of-flight mass analyser. Traditionally only the image of one mass-to-charge ratio can be obtained in a single acquisition, which limits its applicability. However, the development of event-triggered sensors, such as CMOS-based cameras, revives the microscope MSI method by allowing multi-mass imaging. Therefore, the challenges facing microscope have MSI shifted to improving its mass resolution, effective mass range, and mass accuracy. This thesis proposes effective solutions to each of them, and thus significantly improves the performance and applicability of microscope MSI. To increase the mass range, two modified post-extraction differential acceleration (PEDA) techniques, double-field PEDA and time-variable PEDA, were used to demonstrate mass-resolved stigmatic imaging over a broad m/z range. In double-field PEDA, a potential energy cusp was introduced into the ion acceleration region of an imaging mass spectrometer, creating two m/z foci that were tuned to overlap at the detector plane. This resulted in two focused m/z distributions that stretched the mass-resolved window with m/Δm >= 1000 to 165 Da without any loss in image quality; a range that doubled the 65 Da achieved under similar conditions using the original PEDA technique. In time-variable PEDA, a dynamic pulsed electric field was used to maximize the effective mass range of PEDA. By simultaneously focusing ions between 300 to 700 m/z using an exponentially rising voltage pulse, time-variable PEDA provides an effective mass range more than six times wider than the original PEDA method. Although reflectrons are widely used to improve the mass resolving power of ToF-MS, incorporating them in a microscope MSI instrument is novel. A reflectron MSI instrument was designed and implemented. Simulations demonstrated that one-stage gridless reflectrons were more compatible with the spatial imaging goal of the microscope MSI instrument than the gridded reflectrons. Preliminary experimental results showed that coupling the gridless reflectron with single-field PEDA achieved a mass resolution above 8,000 m/Δm while keeping a spatial resolution of 20 um. In conclusion, the gridless reflectron was able to triple the mass resolving power without losing any spatial imaging power. The poor mass accuracy hurdle was overcome by machine learning algorithms, which can construct clinical diagnostic models that recognise the peak pattern of biological mass spectra and classify them accurately without knowing the actual mass of each peak. After a proof of concept "experiment", where the mass spectra of dye molecules were classified by various learning algorithms, three pairs of datasets (ovarian cancer, prostate cancer, chronic fatigue and their respective controls) were used to build classifiers that accurately distinguish blood samples from controls. Possible biomarkers were also discovered by evaluating the importance of each m/z feature, which may assist further studies.

Ce travail de thèse porte sur la réalisation de l'électronique d'un spectromètre de masse à temps de vol, sur la réalisation et les tests au vide d'un prototype embarquable sur satellite. Un effort particulier a été nécessaire pour diminuer au maximum la masse et la consommation électrique du spectromètre, ce qui a conduit au développement de circuits nouveaux.<br />Le travail réalisé au cours de cette thèse porte en premier lieu sur l'électronique de la chaîne de mesure qui a été conçue dans un souci de modularité. Un spectromètre de masse complet de type « réflectron » a ensuite été conçu, simulé puis développé. Le prototype construit, qui utilise l'électronique développée, a été soumis à des flux d'ions de masses et d'énergies différentes dans les chambres à vide du CESR. Ses performances mesurées valident les principes mis en œuvre et démontrent qu'un spectromètre de masse identique peut être embarqué avec profit sur satellite, tant dans le cadre de missions planétaires que solaires.

Laser-Ionization Time-of-Flight Mass Spectrometry (LI-TOF-MS) is a sophisticated tool for the molecular-weight determination and structural characterization of a variety of molecules. Advances in instrumentation and ionization methods have recently expanded its role in the analysis of high-mass analytes. Large multimetallic complexes, which are efficient solar-energy converters, rely heavily on their chemical structure for optimum operation. Molecular mass determinations of these multimetallic complexes have been problematic due to their lability and high molecular weights. This thesis describes the characterization of a LI-TOF-MS instrument and confirmation of theoretical time-of-flight mass-separation principles. Several test cases demonstrate the instrument's proper operation and calibration for a wide mass range of analytes. Mass spectral results of three organometallic compounds: i. [Ir(dpp)₂Cl₂](PF₆), ii. {[(bpy)₂Ru(dpp)]₂IrCl₂}(PF₆)₅, and iii. {[(bpy)₂Ru(dpp)]₂RuCl₂}(PF₆)₅ under a variety of laser ionization and sample preparation conditions are compared. A complete structural characterization of the monometallic complex, [Ir(dpp)₂Cl₂](PF₆), is presented. The two trimetallic analytes fragmented easily, but significant components of the molecules are successfully identified. After optimizing the ionization and analytical procedure, LI-TOF-MS proved useful in the analysis of high molecular mass metal complexes. / Master of Science

Diese Dissertation handelt vom metastabilen Zerfall und von der Oberflächenwechselwirkung im hyperthermalen Energiebereich relativ schwach gebundener molekularer Kohlenmonoxid und Kohlendioxid Clusterkationen mit einer Edelstahloberfläche und einer Siliziumoberfläche. Im Rahmen dieser Arbeit wurde ein hierfür geeignetes spezielles Flugzeitmassenspektrometer entwickelt und aufgebaut. Entwurf, numerische Optimierung der Auflösung, ionenoptische Simulationen und Aufbau der jeweiligen Komponenten wie Elektronenquellen, Beschleuniger, Ablenkplatten, Massenfilter und Reflektron werden detailliert beschrieben. Das entwickelte Flugzeitmassenspektrometer besitzt mit einer kompakten Gesamtfluglänge von ~1.5m eine hohe Massenauflösung von m/Delta m = 3000. Es bietet die Möglichkeit, eine Massentrennung von Clusterionen mit einer Größe von bis zu n = 190 vorzunehmen. Diese massenselektierten Clusterionen können daraufhin auf metastabilen Zerfall und auf ihre Wechselwirkung mit einer Oberfläche untersucht werden. Dazu wurden Kohlendioxid-Clusterionen mit n / This thesis deals with the metastable decay and the surface scattering in the hyperthermal energy range of relatively weakly bound molecular cluster cations. With carbon monoxide and carbon dioxide two related model systems were chosen for a systematic size dependent study. Surface impact experiments were carried out with stainless steel and silicon surfaces. Results were obtained by a new, reflectron time-of-flight mass spectrometer (Re-TOFMS). Additional to the experimental data we present in this work a detailed description of the instrumental design considerations, numerical optimization, ion optical simulations. Hence each ion optical component like electron guns, accelerator, deflector, mass gate and reflectron are described. Despite the compact dimensions with a total flight length of ~1.5m the developed instrument possesses a high mass resolution above m/Delta m = 3000. Additionally it offers the possibility to perform mass separation of big cluster ions with sizes n

Many space probes have conducted in situ explorations of asteroids, in recent decades, intent on identifying evidence of the solar system's earliest processes of formation within the asteroids' interiors. Several future asteroid missions are planned, among which include ESA's Hera mission to explore the Didymos binary asteroid pair. An ion mass analyzer is currently being designed at the Swedish Institute of Space Physics for use as part of the Hera mission. This thesis aims to optimize the instrument such that each of its parameters meets the requirement for performance. A computer simulation is used to calculate the trajectories of low-energy ions inside the instrument, where the electrostatic potential are imposed by grids and electrodes embedded inside the instrument. From the data analysis of the simulation results, the performance for each parameter can be derived. By changing the settings of the grids and electrodes (e.g., positions and voltages), the instrument parameters are to be optimized. Two tasks are set up in this project--- the first task is to optimize the focusing system of the incoming ions at the instrument's entrance, and the second task is to investigate the reflectron system so that the mass resolution of the instrument can be optimized via reducing the spread of the ions' time of flight spectra. The focusing system is found to already be optimized, but instead, a relation between its position of the grid at the instrument's entrance and the instrument's performance is derived. The method of and parameters for optimization within the reflectron are extensively tested individually during this project. Although several performances in each trial from the reflectron analysis cannot meet at least one of the requirements, enough scenarios are examined such that every parameter tested ends with a value suitable to be applied individually to optimize the ion mass analyzer. The findings from the individual tests done in this project can be applied to further optimization, particularly to optimize multiple parameters simultaneously in the near future.

In this dissertation, different approaches have been employed to address the quest of understanding the formation and growth mechanisms of carbon-containing molecular ions with relevance to astrochemistry. Ion mobility mass spectrometry and DFT computations were used to investigate how a second nitrogen in the pyrimidine ring will affect the formation of a covalent bond between the benzene radical cation and the neutral pyrimidine molecule, after it was shown that a stable covalent adduct can be formed between benzene radical cation and the neutral pyridine. Evidence for the formation of a more stable covalent adduct between the benzene radical cation and the pyrimidine is reported here. The effect of substituents on substituted-benzene cations on their solvation by an HCN solvent was also investigated using ion mobility mass spectrometry and DFT computations were also investigated. We looked at the effect of the presence of electron-withdrawing substituents in fluorobenzene, 1,4 di- fluorobenzene, and benzonitrile on their solvation by up to four HCN ligands, and compared it to previous work done to determine the solvation chemistry of benzene and phenylacetylene by HCN. We report here the observed increase in the binding of the HCN molecule to the aromatic ring as the electronegativity of the substituent increased. We also show in this dissertation, DFT calculations that reveal the formation of both hydrogen-bonded and electrostatic isomers, of similar energies for each addition to the ions respectively. The catalytic activity of the 1st and 2nd row TM ions towards the polymerization of acetylene done using the reflectron time of flight mass spectrometry and DFT calculations is also reported in this dissertation. We explain the variation in the observed trend in C-H/C-C activity of these ions. We also report the formation of carbide complexes by Zr+, Nb+, and Mo+, with the acetylene ligands, and show the thermodynamic considerations that influence the formation of these dehydrogenated ion-ligand complexes. Finally, we show in this dissertation, a novel ionization technique that we employed to generate ions that could be relevant to the interstellar and circumstellar media using the reflectron time of flight mass spectrometry.