This thesis concerns multi-ionization coincidence measurements of atoms and small molecules using a magnetic bottle time-of-flight (TOF) spectrometer designed for multi-electron coincidence studies. Also, a time-of-flight mass spectrometer has been used together with the TOF electron  spectrometer for electron-ion coincidence measurements. The multi-ionization processes have been studied by employing a pulsed discharge lamp in the vacuum ultraviolet spectral region and synchrotron radiation in the soft X-ray region. The designs of the spectrometers are described in some detail, and several timing schemes suitable for the light sources mentioned above are presented. Studies have been performed on krypton, molecular oxygen, carbon disulfide and a series of alcohol molecules. For the latter, double ionization spectra have been recorded and new information has been obtained on the dicationic states. A recently found rule-of-thumb  and quantum chemical calculations have been used to quantify the effective distance of the two vacancies in the dications of these molecules. For Kr, O2, and CS2, single-photon core-valence spectra have been obtained at the synchrotron radiation facility BESSY II in Berlin and interpreted on the basis of quantum chemical calculations. These spectra show a remarkable similarity to conventional valence photoelectron spectra. Spectra of triply charged ions were recorded, also at BESSY II, for Kr and CS2 by measuring, in coincidence, all three electrons ejected. The complex transition channels leading to tricationic states were mapped in substantial detail for Kr. It was found that for 3d-ionized krypton, the tricationic states are dominantly populated by cascade Auger decays via distinct intermediate states whose energies have been determined. The triple ionization spectra of CS2 from the direct double Auger effect via S2p, S2s and C1s hole states contain several resolved features and show selectivity based on the initial charge localisation and on the identity of the initial state.

Imaging mass spectrometry (MS) analysis allows scientists the ability to obtain spatial and chemical information of analytes on a wide variety of surfaces. The ability to image biological analytes is an important tool in many areas of life science research, including: the ability to map pharmaceutical drugs in targeted tissue, to spatially determine the expression profile of specific proteins in healthy vs. diseased tissue states, and to rapidly interrogate biomolecular microarrays. However, there are several avenues for improving the imaging MS experiment for biological samples. Three significant directions this work addresses include: (1) reducing chemical noise and increasing analyte identification by developing sample preparation methodologies, (2) improving the analytical figures of merit (i.e., spatial resolution, analysis time) by implementing a spatially dynamic optical system, and (3) increasing both mass spectral resolution and ion detection sensitivity by modifying a commercial time-of-flight (TOF) MS. Firstly, sample methodology schemes presented in these studies consist of obtaining both ?top-down? and ?bottom-up? information. In that, both intact mass and peptide mass fingerprinting data can be obtained to increase protein identification. This sample methodology was optimized on protein microarrays in preparation for bio tissue analysis. Other work consists of optimizing novel sample preparation strategies for hydrated solid-supported lipid bilayer studies. Sample methods incorporating nanomaterials for laser desorption/ionization illustrate the ability to perform selective ionization of specific analytes. Specifically, our results suggest that silver nanoparticles facilitate the selective ionization of olefin containing species (e.g., steroids, vitamins). Secondly, an advanced optical design incorporating a spatially dynamic optical scheme allows for laser beam expansion, homogenization, collimation, shaping, and imaging. This spatially dynamic optical system allows user defined beam shapes, decreases analysis times associated with mechanical movement of the sample stage, and is capable of increasing the MS limits of detection by simultaneously irradiating multiple spots. Lastly, new data acquisition strategies (multiple anode detection schemes) were incorporated into a commercial time-of-flight mass spectrometer to increase both sensitivity and resolution in a matrix assisted laser desorption/ionization mass spectrometer. The utility of this technique can be applied to many different samples, where high mass spectral resolution allows for increased mass measurement accuracy.

A wide range of organic compounds are released from building and furnishing products and these have the potential to adversely affect indoor air quality. There are growing international requirements for testing and controlling these emissions for the protection of public health. The test methods require specialist analytical chemistry facilities based on thermal desorption/gas chromatography/mass spectrometry (TD/GC/MS). This project has addressed the need for better performance and greater automation of the analysis, as well as development of simpler screening tests. A variety of products were tested using screening techniques, with an emission cell method being used as a reference test. Short duration tests, using a micro-scale chamber at slightly elevated temperature, were shown to have the potential to predict emissions occurring during longer term reference tests. Multi-sorbent air sampling tubes, that have the potential to extend the volatility range of compounds determined by a single TD/GC/MS analysis, were compared with Tenax TA tubes specified by current standard methods. This showed no difference in performance for the range of compounds for which Tenax is optimal, with improved performance for a number of more volatile compounds. The determination of formaldehyde was investigated using 2-hydroxymethylpiperidine as a derivatising agent, followed by TD/GC/MS. The results showed the possibility of this method being developed as an alternative to the current standard method that involves solvent elution and liquid chromatography. The performance of a newly developed time-of-flight mass spectrometer was compared with a standard quadrupole instrument. This showed its potential, with the use of re-collection, to extend the concentration range of compounds quantified from a single air sample, of particular benefit for the determination of carcinogens. New compound identification software was applied to increase automation of analysis of the TD/GC/MS data. Good correlation with manual processing was achieved, demonstrating the possibility of routine application to material emissions testing.

L'identification des micro-organismes reposait jusqu'à présent sur l'étude des caractères culturaux et biochimiques de chaque espèce. Depuis quelques années, la spectrométrie de masse de type Matrix Assisted Laser Desorption/Ionization Time Of Flight (MALDI-TOF) s'est développée dans les laboratoires de microbiologie clinique. Cette nouvelle technologie permet de réaliser très rapidement et à moindre coût un diagnostic d'espèce sur des colonies de bactéries ou de champignons isolées sur des milieux de culture solides.Dans un premier temps, nous avons montré que cette technologie permet de réaliser une identification des germes isolés en milieu liquide, comme les flacons d'hémoculture au cours des bactériémies par exemple. Ce dépistage se fait directement à partir du flacon positif, sans attendre l'isolement des colonies sur milieu solide. Ce diagnostic disponible dès le premier jour permet d'adapter l'antibiothérapie au phénotype de résistance habituel de l'espèce.Dans un deuxième temps, nous avons cherché à identifier la nature des biomarqueurs utilisés pour l'identification des espèces bactériennes, en prenant comme exemple la bactérie pathogène Neisseria meningitidis. La comparaison du génome et du protéome des souches entièrement séquencées a permis de mettre en évidence la nature exacte des protéines impliquées dans le diagnostic d'espèce. Par ailleurs, les protéines ribosomales étant majoritaires et pouvant servir d'outil épidémiologique, nous avons constaté que la mise en évidence de leurs variations sur le spectre de masse rend la différenciation de souches au sein d'une même espèce possible, en adaptant la méthode d'analyse. Enfin, nous avons présenté des résultats préliminaires encourageants sur l'exploitation du caractère constant de certaines protéines ribosomales visibles directement sur le spectre de masse, permettant de différencier des espèces très proches, comme Streptococcus pneumoniae et Streptococcus mitis.

No description available.

In the frame of this thesis, a new experimental setup for the measurement of the energy loss of carbon ions at maximum stopping power in a hot laser-generated plasma has been developed and successfully tested. In this parameter range where the projectile velocity is of the same order of magnitude as the thermal velocity of the plasma free electrons, large uncertainties of up to 50% are present in the stopping-power description. To date, no experimental data are available to perform a theory benchmarking. Testing the different stopping theories is yet essential for inertial confinement fusion and in particular for the understanding of the alpha-particle heating of the thermonuclear fuel. Here, for the first time, precise measurements were carried out in a reproducible and entirely characterized beam-plasma configuration. It involved a nearly fully-stripped ion beam probing a homogeneous fully-ionized plasma. This plasma was generated by irradiating a thin carbon foil with two high-energy laser beams and features a maximum electron temperature of 200 eV. The plasma conditions were simulated with a two-dimensional radiative hydrodynamic code, while the ion-beam charge-state distribution was predicted by means of a Monte-Carlo code describing the charge-exchange processes of projectile ions in plasma. To probe at maximum stopping power, high-frequency pulsed ion bunches were decelerated to an energy of 0.5 MeV per nucleon. The ion energy loss was determined by a time-of-flight measurement using a specifically developed chemical-vapor-deposition diamond detector that was screened against any plasma radiation. A first experimental campaign was carried out using this newly developed platform, in which a precision better than 200 keV on the energy loss was reached. This allowed, via the knowledge of the plasma and of the beam parameters, to reliably test several stopping theories, either based on perturbation theory or on a nonlinear T-Matrix formalism. A preliminary analysis suggests that the energy deposition at maximum stopping power is significantly smaller than predicted, particularly, by perturbation approaches.

Free-electron lasers provide high intensity pulses with femtosecond duration and are ideal tools in the investigation of ultrafast processes in materials. Illumination of any material with such pulses creates extreme conditions that drive the sample far from equilibrium and rapidly convert it into high temperature plasma. The dynamics of this transition is not fully understood and the main goal of this thesis is to further our knowledge in this area. We exposed a variety of materials to X-ray pulses of intensities from 1013 to above 1017 W/cm2. We found that the temporal evolution of the resulting plasmas depends strongly on the wavelength and pulse intensity, as well as on material related parameters, such as size, density, and composition. In experiments on atomic and molecular clusters, we find that cluster size and sample composition influence the destruction pathway. In small clusters a rapid Coulomb explosion takes place while larger clusters undergo a hydrodynamic expansion. We have characterized this transition in methane clusters and discovered a strong isotope effect that promotes the acceleration of deuterium ions relative to hydrogen. Our results also show that ions escaping from exploding xenon clusters are accelerated to several keV energies. Virus particles represent a transition between hetero-nuclear clusters and complex biological materials. We injected single mimivirus particles into the pulse train of an X-ray laser, and recorded coherent diffraction images simultaneously with the fragmentation patterns of the individual particles. We used these results to test theoretical damage models. Correlation between the diffraction patterns and sample fragmentation shows how damage develops after the intense pulse has left the sample. Moving from sub-micron objects to bulk materials gave rise to new phenomena. Our experiments with high-intensity X-ray pulses on bulk, metallic samples show the development of a transient X-ray transparency. We also describe the saturation of photoabsorption during ablation of vanadium and niobium samples. Photon science with extremely strong X-ray pulses is in its infancy today and will require much more effort to gain more knowledge. The work described in this thesis represents some of the first results in this area.

A back scatter time of flight neutron spectrometer consisting of two scintillation detectors is simulated in Geant4 to examine whether it is possible to perform a proof of concept test at the NESSA facility at Uppsala University. An efficiency of ε = 2.45 · 10^-6 is shown to be large enough for a neutron generator intensity of 1.9 · 10^10 neutrons per second to achieve a minimal required signal count rate of 10000 counts per hour. A corresponding full width at half maximum energy resolution of 8.3% is found. The background in one of the detectors is simulated in MCNP and found to be a factor 62 larger than the signal for a given set of pulse height thresholds in the detectors. Measures to increase the signal to background ratio are discussed and an outlook for future work concerning testing the spectrometer at NESSA is presented.

In the field of physical chemistry, the relatively recently developed technique of velocity-map imaging has allowed chemical dynamics to be explored with a greater depth than could be previously achieved using other methods. Capturing the scattering image associated with the products resulting from fragmentation of a molecule allows the dissociative pathways and energy landscape to be investigated. In the study of particle physics, the neutron has become an irreplaceable spectroscopic tool due to the unique nature of the interaction with certain materials. Neutron spectroscopy is a non-destructive imaging technique that allows a number of properties to be discerned, including chemical identification, strain tensor measurements and the identification of beneath the sample surface using radiography and tomography. In both of these areas, as well as a multitude of other disciplines, a flight tube is used to separate particles, distinguishing them based upon their mass in the former case and their energy in the latter. The experiments can be vastly enhanced by the ability to record both the position and arrival time of the particle of interest. This thesis describes several new developments made in instrumentation for experiments involving time-of-flight particle imaging. The first development described is the construction of a new velocity-map imaging instrument that utilises electron ionisation to perform both steps of molecular fragmentation and ionisation. Data from CO2 is presented as an example of the ability of the instrument, and a preliminary analysis of the images is performed. The second presented project is the design of a time-resolved and position-resolved detector developed for ion imaging experiments. The hardware, software and firmware are described and presented alongside data from a variety of the experiments showcasing the breadth of investigations that are possible using the sensor. Finally, the modifications made to the detector to allow time-resolved neutron imaging are detailed, with an in-depth description of the various proof-of-concept experiments carried out as part of the development process.

Esta tese teve por objetivo, desde seu início, investigar as propriedades elétricas de um dispositivo ITO/PEDOT:PSS/P3HT:PCBM/Ca/Al, o qual é uma estrutura bem conhecida de célula solar orgânica do tipo de heterojunção de volume (bulk-heterojunction – BHJ), e com isso dar uma contribuição à melhora de seu desempenho. Porém, o primeiro passo foi introduzir no Grupo de Polímeros Bernhard Gross, um método eficaz de produzir células solares do tipo BHJ com boa eficiência e reprodutibilidade. Esse primeiro desafio foi alcançado com sucesso. A eficiência (η) de um dispositivo fotovoltaico de multicamadas depende de muitos fatores. Dentre eles, uma boa superposição entre o espectro solar e a curva de absorção da camada absorvedora, uma excelente conversão da energia luminosa em portadores de carga, um eficiente processo de condução e uma perda mínima por recombinação e armadilhamento de portadores. Além disso, a compatibilidade eletrônica entre as interfaces tem um papel fundamental na definição na tensão de circuito aberto (VOC), no valor da corrente de curto-circuito (JSC), e no fator de preenchimento (FF). Baseado nesses efeitos, realizamos uma série de medidas experimentais, que auxiliado por um modelo teórico proporcionaram um estudo detalhado da evolução em função da temperatura da mobilidade dos portadores (μ) e de seu tempo de vida (τ). Os principais experimentos nessa tese foram realizados em diferentes temperaturas (entre 100 e 340 K). Foram eles: medidas de fotocorrente - Jph(V), a técnica de foto-CELIV, e medidas de transiente de fotovoltagem (TPV). Em paralelo, desenvolvemos o modelo teórico para a descrição analítica de Jph(V) que assumiu contatos não-injetores e que o livre caminho médio (w = μτF) de elétrons e buracos eram iguais (F é o campo elétrico). Nos ajustes teórico/experimental usamos a probabilidade de dissociação dos estados de transferência de carga (P) e o produto μτ como parâmetros de ajuste. A condição na qual o livre caminho médio é maior que a espessura da amostra (w >> L) reproduz a corrente de saturação reversa, Jsat = qGPLG é a taxa de geração dos éxcitons. Para w << L, a fotocorrente varia linearmente com o livre caminho médio, ou seja, J(F) = qGPμτF. A comparação entre os resultados experimentais e os teóricos permitiram, além da obtenção da evolução das grandezas μ e τ com a temperatura, estabelecer uma relação efetiva entre os parâmetros da célula (η, JSC, e FF) e as propriedades elétricas da camada ativa P3HT:PCBM. As medidas termo-mecânicas (DMA) forneceram informações adicionais sobre mudanças estruturais da camada ativa, as quais foram correlacionadas com variações dos parâmetros da célula e com fatores de perda. Finalmente, medidas de tempo-de-voo (TOF) e de CELIV foram realizadas para estudos mais detalhados sobre mecanismos de transporte ao longo da camada ativa, a efeitos de injeção pelos eletrodos, e para o entendimento de efeitos de degradação pela ação do oxigênio. / This thesis aims to investigate electrical characteristics of an ITO/PEDOT:PSS/P3HT:PCBM/Ca/Al device, which is a well-known structure of a bulk-heterojunction (BHJ) organic solar cell, and to contribute to improve its performance. However, the first step was to introduce in the Group of Polymer Bernhard Gross an effective method for producing BHJ solar cells, manufacturing thus devices exhibiting excellent performance and reproducibility. This thesis aims to investigate electrical characteristics of an ITO/PEDOT:PSS/P3HT:PCBM/Ca/Al device, which is a well-known structure of a bulk-heterojunction (BHJ) organic solar cell, and to contribute to improve its performance. However, the first step was to introduce in the Group of Polymer Bernhard Gross an effective method for producing BHJ solar cells, manufacturing thus devices exhibiting excellent performance and reproducibility. This goal was successfully achieved. The good efficiency (η) of a multilayer photovoltaic cell depends on many factors, including good overlap between the solar spectrum and the light absorbing layer, an excellent conversion of the absorbed light energy in pairs of electronic carriers, efficient charge transport and the minimum losses by recombination or by the action of deep traps for the carriers. Furthermore, the compatibility between electronic interfaces plays a crucial role in defining the open-circuit voltage (VOC) and the value of short-circuit current (JSC), and on the fill factor (FF). Anchored on these effects, we carried out a series of experiments, aided by a theoretical modeling, which provided a detailed study of the temperature evolution of fundamental electric quantities such as carrier mobility (μ) and its lifetime (τ). These studies were performed with the help of different experiments: photocurrent in function of the applied voltage  Jph(V), Photo-CELIV technique, and Transient Photovoltage (TPV) measurements, which were carried out at several temperatures in the 100 to 340 K range. In parallel, we developed an analytical model for Jph(V) that assumed non-injecting contacts and equal mean-free-paths for electrons and holes. The theoretical/experimental entities used as fitting parameters were the charge-transfer-state dissociation probability (P) and the μτ product. The condition in which the mean-free-path (w = μτF) is higher the sample thickness (L), the model reproduces the experimental reverse saturation current, Jsat = qGPL, which is coincident with the experimental value. F is the internal electric field and G is the generation rate of excitons by the absorbed light. When w << L, J(F) = qGPμτF, which is also coincident with experimental behavior. The confrontation between the experimental results and the theoretical model provided, in addition to the study of the evolution of μ and τ with temperature, to establish a more effective relationship between the parameters (η, JSC, e FF) of the cell and the electrical properties of the P3HT:PCBM active layer. Thermomechanical analysis (DMA) provided additional information of structural changes of active layer, which can be correlated with change in the loss factor and in the cell parameters. Finally, Time-of-Flight (TOF) and CELIV techniques were used in the more accurate study of charge transport along the active layers, effects of injection by the electrodes, and the degradation effect caused by oxygen.