Neste trabalho, as técnicas de difração de raios X (DRX) e espectroscopia de absorção de raios X (XAS) foram utilizadas respectivamente na caracterização da ordem estrutural de longo e curto alcance no sistema cerâmico Pb1-xLaxTiO3 (PLTX) com x variando entre 0 e 30% de lantânio e no sistema cerâmico Pb1-xBaxZr0,65Ti0,35O3 (PBZTX) com x variando entre 0 e 40% de bário. O principal objetivo deste trabalho foi correlacionar as informações estruturais em ambos os sistemas com a mudança de comportamento ferroelétrico normal para um ferrolétrico relaxor que ocorre a medida que o átomo de chumbo é substituído pelos átomos lantânio (PLTX) e bário (PBZTX). Os resultados de XAS mostram em todas as amostras caracterizadas como ferroelétricos normais e em temperaturas abaixo e acima da transição de fase (Tc) que o átomo de titânio está sempre deslocado de sua posição centro-simétrica dentro do octaedro TiO6. O mesmo resultado foi observado nas amostras relaxoras acima e abaixo da temperatura de máximo da permissividade dielétrica relativa (Tm). Os resultados de XAS mostram que tanto para ambos os sistemas que o grau de desordem a nível local não depende da amostra ser um material ferroelétrico normal ou relaxor e de sua estrutura cristalina a longa distância ser de alta ou de baixa simetria. Por outro lado, os resultados de DRX mostram para as amostras ferroelétricas normais uma estrutura tetragonal abaixo de Tc e uma estrutura cúbica em temperaturas acima de Tc. Nas amostras que apresentam propriedades relaxoras (PLT30 e PBZT40), em temperaturas acima do máximo da permissividade dielétrica relativa (Tm), os resultados de DRX mostram para ambos os sistemas uma estrutura cúbica. Para a amostra relaxora do sistema PBZTX (PBZT40), o resultado de DRX mostra que a estrutura é cúbica em temperaturas bem acima e bem abaixo de Tm. Entretanto, para a amostra relaxora do sistema PLTX (PLT30), é observada uma transição de fase cúbica (acima de Tm) para tetragonal (abaixo de Tm). Uma relação entre os resultados estruturais obtidos por ambas as técnicas e as propriedades ferroelétricas exibidas por este conjunto de amostras é apresentada. O uso simultâneo das técnicas de DRX e XAS mostrou ser complementar levando à obtenção de resultados estruturais ainda não presentes na literatura especializada. / In the present work, X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) techniques were used in order to investigate, respectively, the long and short range order of Pb1-xLaxTiO3 (PLTX with 0.0 <= x <= 0.30) and Pb1-xBaxZr0,65Ti0,35O3 (PBZTX with 0.0 <= x <= 0.40) ferroelectric ceramic systems. The main objective of this work was to correlate the structural information with the electrical properties presented as a function of the sample composition and the temperature. XAS results shows that for the samples characterized as normal ferroelectric and above or below the phase transition temperature (Tc), the titanium atoms are always displaced from its centre symmetric position on the TiO6 octahedra. The same result was observed for the samples characterized as relaxors below and above the maximum of the relative dielectric permitivitty (Tm). XAS results show than for both systems that the local disorder did not depends if the sample is a relaxor or a normal ferroelectric or if the sample presents a lower or higher symmetric crystalline structure. On the other hand, XRD results show that the normal ferroelectric samples present, respectively, a tetragonal and a cubic structure below and above Tc. On the samples that presents a relaxor behavior (PLT30 and PBZT40), above the temperature of maximum of the relative dielectric permitivitty (Tm), XRD results show a cubic structure for both samples. Below this maximum, for the PBZT40 sample, the structure was also characterized as cubic. However, for the PLT30 sample, XRD results show a phase transition from a cubic (above Tm) to a tetragonal structure (below Tm). A relationship between structural information and the ferroelectric properties are presented. The simultaneous application of DRX and XAS techniques provide interesting and new structural information not yet presented on the specialized literature.

Le cuivre est un élément chimique, nocif pour la matière vivante, qui peut s'associer sous de nombreuses formes aux constituants organiques et inorganiques des sols. A une échelle macroscopique, les modélisations thermodynamiques, souvent surparamétrées, sont insuffisantes pour conclure sur la nature des formes présentes. La spectroscopie d'absorption X (XAS) réalisée avec des rayons focalisés sur quelques micro-m² permet d'accéder à cette information. A cette échelle micrométrique, la variabilité spécifique des formes du cuivre d'un point d'analyse à un autre se traduit par un changement du signal mesuré en micro-XAS. L'analyse en Composantes Principales (ACP) permet alors en théorie de dénombrer les espèces pures. Ces techniques ont été utilisées pour caractériser les formes cuprifères d'une part dans des rizières contaminées par une exploitation minière (MAMUT, MALAISIE) et d'autre part dans un bassin d'infiltration d'eaux de ruissellement (CHASSIEU, FRANCE). Les présences de cuivre associé avec la matière organique et sous formes métallique, de chalcopyrite et de cristaux localement spécifiques ont été mises en évidence. Néanmoins, en raison de la faible fiabilité des indicateurs existants, le nombre total des espèces cuprifères n'a pu être que majoré par ACP. Ce problème a été surmonté par la mise au point d'un nouvel indicateur évalué statistiquement sur des mélanges de composition connue et dont la précision sur le nombre d'espèces est de ± 1 dans les cas les plus défavorables. / Copper is a chemical element, harmful for the living matter, which may be associated under different forms with organic and inorganic constituents of soils. At a macroscopic scale, thermodynamic modelings, often over-parameterized, are insufficient to conclude on the nature of these forms. X-ray absorption spectroscopy (XAS) performed with rays focused on a few micro-m² allows the access at this information. At this micrometer scale, the specific variability of copper forms from one point of analyze to another induces changes on the measured micro-XAS signal. In theory, Principal Component Analysis (PCA) enables the enumeration of pure species. These techniques have been used to characterize the copper forms on the one hand in paddy fields contaminated by mining (MAMUT, MALAYSIA) and on the other hand in an infiltration basin of runoff waters (CHASSIEU, FRANCE). Copper associated with organic matter, metallic copper, chalcopyrite and local specific copper crystals have been identified. However, due to the low reliability of existing indicators, the total number of copper species has only been limited by ACP. This problem was overcome by the development of a new indicator statistically evaluated on known composition mixtures and whose accuracy on the number of species is ± 1 in the worst cases. STAR Date de soutenance : 3 octobre 2011 Thèse sur travaux: non

Neste trabalho, as técnicas de difração de raios X (DRX) e espectroscopia de absorção de raios X (XAS) foram utilizadas respectivamente na caracterização da ordem estrutural de longo e curto alcance no sistema cerâmico Pb1-xLaxTiO3 (PLTX) com x variando entre 0 e 30% de lantânio e no sistema cerâmico Pb1-xBaxZr0,65Ti0,35O3 (PBZTX) com x variando entre 0 e 40% de bário. O principal objetivo deste trabalho foi correlacionar as informações estruturais em ambos os sistemas com a mudança de comportamento ferroelétrico normal para um ferrolétrico relaxor que ocorre a medida que o átomo de chumbo é substituído pelos átomos lantânio (PLTX) e bário (PBZTX). Os resultados de XAS mostram em todas as amostras caracterizadas como ferroelétricos normais e em temperaturas abaixo e acima da transição de fase (Tc) que o átomo de titânio está sempre deslocado de sua posição centro-simétrica dentro do octaedro TiO6. O mesmo resultado foi observado nas amostras relaxoras acima e abaixo da temperatura de máximo da permissividade dielétrica relativa (Tm). Os resultados de XAS mostram que tanto para ambos os sistemas que o grau de desordem a nível local não depende da amostra ser um material ferroelétrico normal ou relaxor e de sua estrutura cristalina a longa distância ser de alta ou de baixa simetria. Por outro lado, os resultados de DRX mostram para as amostras ferroelétricas normais uma estrutura tetragonal abaixo de Tc e uma estrutura cúbica em temperaturas acima de Tc. Nas amostras que apresentam propriedades relaxoras (PLT30 e PBZT40), em temperaturas acima do máximo da permissividade dielétrica relativa (Tm), os resultados de DRX mostram para ambos os sistemas uma estrutura cúbica. Para a amostra relaxora do sistema PBZTX (PBZT40), o resultado de DRX mostra que a estrutura é cúbica em temperaturas bem acima e bem abaixo de Tm. Entretanto, para a amostra relaxora do sistema PLTX (PLT30), é observada uma transição de fase cúbica (acima de Tm) para tetragonal (abaixo de Tm). Uma relação entre os resultados estruturais obtidos por ambas as técnicas e as propriedades ferroelétricas exibidas por este conjunto de amostras é apresentada. O uso simultâneo das técnicas de DRX e XAS mostrou ser complementar levando à obtenção de resultados estruturais ainda não presentes na literatura especializada. / In the present work, X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) techniques were used in order to investigate, respectively, the long and short range order of Pb1-xLaxTiO3 (PLTX with 0.0 <= x <= 0.30) and Pb1-xBaxZr0,65Ti0,35O3 (PBZTX with 0.0 <= x <= 0.40) ferroelectric ceramic systems. The main objective of this work was to correlate the structural information with the electrical properties presented as a function of the sample composition and the temperature. XAS results shows that for the samples characterized as normal ferroelectric and above or below the phase transition temperature (Tc), the titanium atoms are always displaced from its centre symmetric position on the TiO6 octahedra. The same result was observed for the samples characterized as relaxors below and above the maximum of the relative dielectric permitivitty (Tm). XAS results show than for both systems that the local disorder did not depends if the sample is a relaxor or a normal ferroelectric or if the sample presents a lower or higher symmetric crystalline structure. On the other hand, XRD results show that the normal ferroelectric samples present, respectively, a tetragonal and a cubic structure below and above Tc. On the samples that presents a relaxor behavior (PLT30 and PBZT40), above the temperature of maximum of the relative dielectric permitivitty (Tm), XRD results show a cubic structure for both samples. Below this maximum, for the PBZT40 sample, the structure was also characterized as cubic. However, for the PLT30 sample, XRD results show a phase transition from a cubic (above Tm) to a tetragonal structure (below Tm). A relationship between structural information and the ferroelectric properties are presented. The simultaneous application of DRX and XAS techniques provide interesting and new structural information not yet presented on the specialized literature.

Le nettoyage laser Nd:YAG Q-switched (1064 nm) confère souvent aux surfaces nettoyées un aspect plus jaune que les autres techniques de nettoyage. Cet effet jaune peut conduire à l’obtention de contrastes de couleur inesthétiques si différentes techniques de nettoyage sont utilisées sur un même ensemble architectural, comme c’est le cas par exemple pour le portail des Valois de la basilique Saint-Denis près de Paris. Une des hypothèses émises pour expliquer le phénomène est que le jaunissement laser serait lié à la présence de résidus d’irradiation nanométriques formés par interaction du faisceau laser avec la salissure, en particulier les croûtes noires gypseuses communément observées sur les monuments en pierre. Dans le cadre de cette thèse, une méthodologie analytique multi-échelle allant jusqu’à l’échelle nanométrique a été développée pour observer et caractériser les composés néoformés responsables de la coloration jaune. Des éprouvettes de croûtes modèles à base d’hématite et de croûtes reconstituées à partir de croûte noire naturelle ont été élaborées. La croûte noire naturelle a été caractérisée pour déterminer les composés susceptibles de réagir au faisceau laser et donc de contribuer au jaunissement. Des oxydes de fer (hématite, magnétite, maghémite) et des cendres volantes silico-alumineuses issues de la combustion du charbon ont ainsi pu être mis en évidence. La nature chimique et structurale des produits de l’irradiation laser des éprouvettes a ensuite été examinée à l’aide d’un panel de techniques incluant entre autres la microscopie électronique à transmission (MET) couplée à la diffraction électronique et aux spectroscopies de rayons X par dispersion d’énergie (EDX) et de perte d’énergie des électrons (EELS). Des nanostructures cristallisées sous forme de nano-sphères et de nano-résidus ont ainsi pu être observées. La caractérisation de la composition chimique à l’échelle nanométrique a permis de révéler la présence de fer dans toutes les nanostructures. Une étude approfondie de la couleur a en outre permis de relier les propriétés colorimétriques du processus de jaunissement à la nature des nano-composés néoformés par irradiation laser. D’autre part, le portail des Valois de la basilique Saint-Denis a été le sujet d’une étude de cas qui est venue complémenter la recherche tout en ancrant l’étude dans la réalité du monde de la conservation des monuments historiques. Enfin des essais de remédiation ont démontré les potentialités de l’utilisation d’un rayonnement UV pour atténuer ou ne pas produire de jaunissement. In fine, ce travail a permis de démontrer que le phénomène de jaunissement laser observé à l’échelle macroscopique est intimement lié à des transformations de matière à l‘échelle nanométrique, induites par l’interaction du rayonnement laser avec les oxydes de fer et les cendres volantes présents dans les encrassements. / Nd:YAG Q-Switched laser cleaning of soiled stone at 1064 nm can sometimes result in yellower appearances than other conventional cleaning techniques. This yellowing effect can lead to unsightly colour contrasts if different cleaning techniques are used on the same architectural complex, as is the case for the Valois Portal of the Saint-Denis basilica near Paris. One argument made to explain the phenomenon is that the laser yellowing is linked to the creation of nano-sized irradiation residues through the laser beam interaction with soiling matter such as black gypseous crusts. In this study, a multi-scale analytical method extending to the nanoscale has been used to observe and characterize the neo-formed compounds accountable for the yellow discoloration. Samples of model crusts containing hematite and reconstituted crusts prepared with natural black crust have been synthetized. The natural black crust has been characterized in order to identify the compounds that may react under the laser beam and thus contribute to the yellowing effect. Iron oxides (hematite, magnetite and maghemite) and aluminosilicate fly-ashes originating from coal combustion have been discovered. The chemical and structural nature of irradiation products has then been investigated by several techniques including in particular transmission electron microscopy (TEM) coupled with electronic diffraction and energy-dispersive X-ray (EDX) and electron energy-loss (EELS) spectroscopies. Iron containing nanostructures crystallized in the form of nano-spheres and nano-residues have been evidenced and characterized. By studying thoroughly the colour, the colorimetric properties of the yellowing process have been linked to the nature of the neo-formed compounds. Furthermore a case study on the Valois Portal has completed the research while setting it within the reality of the conservation world. Finally experiments with UV light have shown the promising potentiality of this tool as a remedy to the yellowing effect. In summary, this study has demonstrated that the yellowing phenomenon observed at the macroscale is intimately linked to matter transformations occurring at the nanoscale, induced by the interaction between the laser beam and the iron oxides and fly-ashes found in black crusts.

Les boîtes quantiques sous formes de nanocristaux semi-conducteurs permettent de réaliser des matériaux à énergie de gap variable, propriété très intéressante pour les composants optoélectroniques. Ce travail est dédié à la création de nanocristaux de silicium dopés enfouis dans SiO2 et de nanocistaux binaires (InAs et GaAs) et ternaires d’InxGa1-xAs enfouis dans Si et à leurs caractérisations structurales, électriques et optiques. La synthèse par faisceaux d’ions permet d’avoir un contrôle de la quantité et de la taille des nanocristaux synthétisés. Des caractérisations structurales ont pu démontrer le dopage des nanocristaux de silicium avec le phosphore et l’arsenic à une concentration atomique moyenne de 8 %. Nous avons également montré la possibilité de moduler la taille et la composition chimique des nanocristaux d’InxGa1-xAs sur une large gamme à l’aide de la dose d’implantation et de la température de recuit. / Semiconductor nanocrystals can be used as quantum dots to produce band gap engineering by varying the nanocrystals size, which is a very interesting property for optoelectronic components. This work is dedicated to the creation of doped silicon nanocrystals embedded in SiO2 and binary (InAs and GaAs) and ternary nanocrystals of InxGa1-xAs embedded in Si and also to investigate their structural, electrical and optical properties. Ion beam synthesis allows a control of the nanocrystals amount and size. Structural characterizations were able to demonstrate the doping of silicon nanocrystals with phosphorus and arsenic at an average atomic concentration of 8 %. We have also shown the ability to modulate the size and the chemical composition of InxGa1-xAs nanocrystals in a large range by varying the implantation dose and the annealing temperature.

Les catalyseurs hétérogènes sont des matériaux complexes dont les structures peuvent être modifiées en cours de fonctionnement. Une meilleure compréhension des relations entre propriétés catalytiques et propriétés structurales est nécessaire pour répondre à de nouveaux enjeux environnementaux et économiques. Seules les caractérisations in situ résolues dans le temps i.e. dans des conditions réelles, permettent d’apporter ces informations. Dans ce travail, nous nous sommes intéressés à la caractérisation operando par spectroscopie d’absorption des rayons X (XAS) résolue dans le temps de deux types de catalyseurs hétérogènes : les catalyseurs Fischer-Tropsch et les catalyseurs d’hydrodésulfuration. Si ces catalyseurs sont connus depuis de nombreuses années, peu de caractérisations sont réalisées in situ ou operando au cours de la réaction.Etant données leurs conditions réactionnelles (haute température et haute pression), la mise en œuvre de ces caractérisations a nécessité tout d’abord la construction des outils nécessaires à la caractérisation in situ de catalyseurs hétérogènes sous haute pression de gaz. Ensuite, nous avons réuni un ensemble cohérent de techniques de caractérisation autour du catalyseur Fischer-Tropsch afin de permettre son étude structurale à différentes échelles : l’ordre local avec le Quick-EXAFS et l’ordre à grande distance avec la diffraction des rayons X. Afin d’observer l’effet de la forme cristalline de la phase active sur les propriétés catalytiques, nous avons pour un même catalyseur, activé selon deux voies d’activation, quantifié son activité au moyen de la spectroscopie Raman et la spectrométrie de masse. D’autre part, la caractérisation simultanée de deux centres métalliques, accessible par le dispositif QEXAFS installé sur la ligne de lumière SAMBA, a permis d’obtenir une description fine des processus d’activation des catalyseurs bimétalliques d’hydrodésulfuration. Notre étude s’est portée, sur la comparaison de catalyseurs de même formulation avec des prétraitements différents (séché/calciné) et de deux catalyseurs promus par des métaux différents : le cobalt et le nickel. / Heterogeneous catalysts are complex material whose structures can change on working conditions. To tackle new environmental and economic issues a better knowledge of the relationship between catalytic and structural properties is needed. Only in situ time resolved characterisations i.e. in real working conditions can provide this information.In this study we worked with operando time-resolved X-ray Absorption Spectroscopy (XAS) on two types of heterogeneous catalysts: Fischer-Tropsch catalysts and hydrodesulfurisation catalysts. If these catalysts have been known for many years, only few characterisations are conducted in situ or operando during the reaction.Given their reaction conditions (high temperature and high pressure), these characterisations involved first the construction of tools for in situ characterisation of heterogeneous catalysts under high pressure of gas. Then we assembled a coherent set of characterisation techniques around the Fischer-Tropsch catalyst to enable the structural study at different scales: the local order with the Quick-EXAFS and long-range order with the X-ray diffraction. To observe the effect on the catalytic properties of the crystalline form of the active phase, we quantified for the same catalyst its activity by Raman spectroscopy and mass spectrometry after activation by two different treatments Besides, simultaneous characterisation of two metal species, accessible by the QEXAFS setup installed on the SAMBA beamline, allowed an accurate description of the activation process of bimetallic catalysts for hydrodesulfurisation. We focused our study on the comparison of catalysts with the same formulation with different pretreatments (dried / calcined) and two catalysts promoted by different metals: cobalt and nickel.

Lanthanide-based nanoparticles can be used in a variety of applications, including biomedical work such as imaging and cancer therapies, and in solar cells. This thesis presents two different potential applications for lanthanide-based nanoparticles and a possible new method for single nanoparticle analysis. Each of the projects presented in this thesis starts from the colloidal synthesis of the nanoparticles and then explores their varying properties, such as size and size distribution, crystallinity, elemental composition, and optical properties. Chapter 1 presents a short introduction to lanthanides and explores their ability to luminesce and upconvert. These optical properties make lanthanide-based nanoparticles attractive in both the visible and near-infrared (NIR) range. Chapter 2 explores the possibility of using β-LaF3:Nd3+ (5%) nanoparticles in a colloidal laser to overcome some issues that solid state lasers face due to thermal effects. A colloidal laser requires small nanoparticles that can emit a useful wavelength and that are dispersed in a high boiling point liquid. In Chapter 3, a cation exchange of ytterbium for yttrium and erbium in water-dispersible β-NaYF4:Er3+ nanoparticles across a polyvinylpyrrolidone (PVP) surface coating was tested as a possible synthesis route for radioactive nanoparticles. Incorporating radioactive materials at the end of a therapy preparation would limit the number of synthesis steps in an isotope laboratory. Chapter 4 presents single-particle analysis of β-NaYF4:Er3+ (50%) nanoparticles using X-ray absorption spectroscopy (XAS) at the Canadian Light Source (CLS). Electron beams in scanning electron transmission microscopes (STEM) can damage the samples, making quantification of nanoparticles challenging. Finally, Chapter 5 discusses some conclusions and suggests possible future work. / Graduate / 0494

The Enhanced Actinide Removal Plant (EARP) located at Sellafield, is a key facility for processing nuclear effluents in the UK. The EARP process decontaminates radioactive waste effluent by inducing the coprecipitation of Fe(III) along with any radionuclides in solution. The resulting radioactive solid phase is then separated from the decontaminated aqueous phase by ultrafiltration processes over several weeks. In the future the EARP facility's role will be expanded to treat effluents produced from nuclear decommissioning activities. However there remains a limited understanding around the mechanisms of radionuclide removal from solution and subsequent sequestration within the solid phase under conditions relevant to such industrial effluent treatment facilities. In this work, the fate of U(VI) and Th(IV) were investigated during the EARP process. XRD and TEM analyses revealed that the solid product from the EARP coprecipitation process was 2-line ferrihydrite which transformed over time to form hematite, with some goethite formation observed in the Th containing system. During this coprecipitation process U was initially removed from solution by adsorption to ferrihydrite as a bidentate, edge-sharing surface complex associated with ternary carbonate complexes. As the U containing system was aged, a maximum range of 61 - 75% U became consistently incorporated within the newly formed hematite phase for a wide range of systems containing 6 orders of magnitude total U:Fe molar ratio. Such a constant proportion of incorporated U suggests that this incorporation occurs during a particle mediated mechanism of hematite growth, such as oriented attachment. Interestingly, Th was removed from solution during the EARP coprecipitation process by a combination of both adsorption and occlusion mechanisms. EXAFS analyses revealed that the local coordination environment of Th associated with the solid phase altered considerably with increased aging time, and correspondingly Th became increasingly recalcitrant to remobilisation over time suggesting the formation of further occluded or even incorporated Th species within the transforming iron (oxyhydr)oxide phases. This thesis progresses the fundamental understanding of radionuclide interactions with iron (oxyhydr)oxide phases during coprecipitation and aging processes under conditions relevant to industrial waste treatment processes such as EARP.

This thesis presents results of theoretical modeling of x-ray and vibrational spectroscopies applied to liquid water and to CO adsorbed on a Ni(100) surface. The Reverse Monte Carlo method is used to search for  water structures that reproduce diffraction, IR/Raman and x-ray absorption by fitting them to experimental data and imposed constraints. Some of the structures are created to have a large fraction of broken hydrogen bonds because recent x-ray absorption and emission studies have been seen to support the existence of such structures. In the fitting procedure a fast way of computing the IR/Raman spectrum for an isolated OH stretch is used, where the frequency is represented by the electric field projected in the direction of the stretch coordinate. This method is critically evaluated by comparing it to quantum chemical cluster calculations. Furthermore, the x-ray emission spectrum of water is investigated, the modeling of which is complicated by the necessity of including vibrational effects in the spectrum calculations due to a dissociative intermediate state. Based on the Kramers-Heisenberg formula a new semi-classical method is developed to include vibrational effects in x-ray emission calculations. The method is seen to work very well for a one-dimensional test system. Moreover, x-ray absorption and emission are implemented in a periodic Density Functional Theory code which is applied to ice and to the surface adsorbate system CO on Ni(100). / Den här avhandlingen presenterar resultat av teoretisk modellering av röntgen- och vibrationella spektroskopier applicerade på flytande vatten och på CO adsorberat på en Ni(100) -yta. Reverse Monte Carlo-metoden används till att söka efter vattenstrukturer som reproducerar diffraktion, IR/Raman, röntgenabsorption och emission genom att anpassa strukturerna till experimentella data samt till pålagda restriktionsvillkor. Vissa av strukturerna är skapade så att de har en stor andel brutna vätebindningar eftersom nya röntgenabsorptions- och emissionsexperiment har setts stödja förekomsten av sådana strukturer. I anpassningsprocessen används en metod för att snabbt beräkna IR/Raman-spektrum för en isolerad OH-stretch, där frekvensen representeras av det elektriska fältet projicerat i stretch-koordinatens riktning.Vi utvärderar kritiskt denna metod genom att jämföra den med kvantkemiska klusterberäkningar. Vidare undersöks vattens röntgenemissionsspektrum, vars modellering kompliceras av nödvändigheten att inkludera vibrationella effekter i spektrumberäkningarna på grund av ett dissociativt intermediärt tillstånd. Baserat på Kramers-Heisenbergformeln utvecklas en ny semiklassisk metod som inkluderar vibrationella effekter. Metoden visar sig fungera mycket väl för ett endimensionellt testsystem. Dessutom implementerar vi röntgenabsorption och emission i en periodisk Täthetsfunktionalteorikod som vi sedan applicerar  på is och på ett ytadsorbatsystem: CO på Ni(100). / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Manuscript. Paper 5: Manuscript. Paper 6: Manuscript.

X-ray spectroscopic experiments, including X-ray absorption spectroscopy (XAS), X-ray emission spectroscopy (XES) and resonant inelastic X-ray scattering (RIXS), were performed in a large energy range (60-9000 eV) on a variety of systems, probing different elements and orbitals. The systems can preferably be divided into three groups: Actinides, copper systems and amorphous materials. We studied oxidation states of Pu in PuO2 using a closed-source experimental setup, developed by us, to lower the safety restrictions associated with such experiments. The presence of Pu with higher oxidation state than Pu(IV) was found in polycrystalline PuO2. This is an important finding since Pu with higher oxidation states has higher solubility affecting the safety of a proposed undeground repository of spent nuclear fuel which can eventually be infiltrated by groundwater. In the proposed underground repository the molecular oxygen will vanish at some point due to microbial activity and mineral oxidation. At this stage sulfur is the most important candidate for causing copper corrosion. We studied Cu films and foils exposed to sulfide solutions at both Cu L2,3, Cu K and S L2,3 edges and found for example that S L2,3 XES is useful for distinguishing between different copper sulfides and Cu Kβ XES can be used to identify monovalent Cu compounds. Amorphous, zirconium containing alloys are potentially useful materials for future nuclear reactors. The electronic structure of such materials was also investigated.