Concrete substructures are often subjected to environmental deterioration, such as sulfate and acid attack, which leads to severe damage and causes structure degradation or even failure. In order to improve the durability of concrete, the High Performance Concrete (HPC) has become widely used by partially replacing cement with pozzolanic materials. However, HPC degradation mechanisms in sulfate and acidic environments are not completely understood. It is therefore important to evaluate the performance of the HPC in such conditions and predict concrete service life by establishing degradation models. This study began with a review of available environmental data in the State of Florida. A total of seven bridges have been inspected. Concrete cores were taken from these bridge piles and were subjected for microstructural analysis using Scanning Electron Microscope (SEM). Ettringite is found to be the products of sulfate attack in sulfate and acidic condition. In order to quantitatively analyze concrete deterioration level, an image processing program is designed using Matlab to obtain quantitative data. Crack percentage (Acrack/Asurface) is used to evaluate concrete deterioration. Thereafter, correlation analysis was performed to find the correlation between five related variables and concrete deterioration. Environmental sulfate concentration and bridge age were found to be positively correlated, while environmental pH level was found to be negatively correlated. Besides environmental conditions, concrete property factor was also included in the equation. It was derived from laboratory testing data. Experimental tests were carried out implementing accelerated expansion test under controlled environment. Specimens of eight different mix designs were prepared. The effect of pozzolanic replacement rate was taken into consideration in the empirical equation. And the empirical equation was validated with existing bridges. Results show that the proposed equations compared well with field test results with a maximum deviation of ± 20%. Two examples showing how to use the proposed equations are provided to guide the practical implementation. In conclusion, the proposed approach of relating microcracks to deterioration is a better method than existing diffusion and sorption models since sulfate attack cause cracking in concrete. Imaging technique provided in this study can also be used to quantitatively analyze concrete samples.

La volonté d'améliorer l'efficacité énergétique des réacteurs nucléaires a motivé de nouvelles solutions dans leur conception. L'une d'elles est l’utilisation d’un réflecteur lourd dans les réacteurs de génération III+ et les futurs réacteurs de génération IV. Lorsque la matière est traversée par des rayons γ, les excitations induites entraînent une élévation de sa température. Ce processus, appelé échauffement γ, est responsable de plus de 90% de la production de chaleur dans la région hors combustible d'un réacteur nucléaire. C’est également le cas dans le réflecteur. Pour simuler l'effet de l’échauffement γ en fonction de la composition du combustible, il faut disposer de données précises sur les γ prompts émis par les différents fragments produits dans le processus de fission. En 2012, une campagne d’expériences inédite, EXILL, a été menée au réacteur de recherche de l'ILL. Un grand nombre de détecteurs HPGe a été placé autour d’une cible fissile et a mesuré les rayons γ émis par la cible alors qu’elle était irradiée par un faisceau intense de neutrons froids. Dans ce travail, nous avons analysé les données obtenues avec des cibles ²³⁵U. Elles nous ont permis d’étudier la désexcitation de plusieurs fragments de fission et plus globalement le processus de fission induite par des neutrons. Dans un premier temps, nous avons utilisé la méthode standard d'analyse par coïncidence γ-γ-γ. Nous avons pu filtrer les données expérimentales, identifier les transitions γ dans des fragments bien produits et calculer leur intensité relative. Les problèmes que nous avons rencontrés concernent le bruit de fond. Les résultats obtenus dépendent de ce choix et présentent donc des problèmes de reproductibilité. Nous avons développé et testé une nouvelle méthodologie d'analyse. Son principe est un balayage des portes de coïncidence selon trois directions, ce qui permet de trouver le bruit de fond le mieux adapté. L'idée principale était finalement de passer d'une méthode "spectroscopique", dont le but est de trouver de nouvelles transitions et des états excités dans un noyau, à une méthode "spectrométrique", qui nous permet d'obtenir plus précisément l’intensité de transitions γ connues, avec une meilleure estimation de leur incertitude. Cela nous a amené à développer un logiciel d'analyse semi-automatique d'ajustement des pics. Divers schémas de calcul de l'intensité des transitions γ ont été également élaborés pour tenir compte des contaminations possibles, selon leur emplacement dans la matrice de coïncidence et leur intensité. La méthode standard et la nouvelle méthode d'analyse ont été comparées pour l'analyse du ¹⁴²Ba. Dans ce travail, nous avons également comparé nos résultats sur quelques noyaux, tel que le ¹⁰⁰Zr, avec des simulations réalisées avec le code FIFRELIN. Ce dernier est un code Monte-Carlo qui simule le processus de fission et la désexcitation des fragments de fission. FIFRELIN utilise plusieurs modèles différents pour décrire ces processus. Nous avons testé le comportement des différents modèles, trouvé les valeurs optimales des paramètres de simulation et testé comment ces configurations reproduisaient les résultats expérimentaux. FIFRELIN n'a pas été en mesure de reproduire simultanément les intensités des transitions γ émises par les fragments de ¹⁰⁰Zr et la multiplicité de neutrons prompts moyennée sur tous les fragments de fission. Cependant, avec des paramètres modifiés, FIFRELIN a fourni localement une multiplicité de neutrons prompts correcte pour les fragments de masse atomique A=100 et des intensités de transition γ bien reproduites pour le noyau de ¹⁰⁰Zr. Nous avons également comparé nos résultats expérimentaux sur les fragments de ¹⁰⁰Zr provenant du processus ²³⁵U(n,f) avec les autres données expérimentales disponibles provenant des expériences sur ²⁴⁸Cm(sf) et ²⁵²Cf(sf), et une autre expérience sur ²³⁵U(n,f). / The desire to improve the fuel efficiency of nuclear reactors has motivated new solutions in their design. One of them is the heavy reflector used in the generation III+ and in the future generation IV reactors. γ-rays passing through matter cause its excitation and temperature rise. It is a process called γ-heating, and it is responsible for more than 90% of the heat production in the non-fuel region of the nuclear reactor. This is also the case of the heavy reflector. To simulate the γ-heating effect in every state of the nuclear reactor it is necessary to have precise data on the prompt γ-rays emitted by different fission fragments produced in the course of the nuclear chain reaction. In 2012, at the research reactor of the ILL, an innovative experiment, called EXILL, was conducted. It produced a large amount of useful data on the de-excitation of the fission fragments. A large number of HPGe detectors were used to study the neutron induced fission process by measuring the emitted γ-rays. Fissile targets were irradiated by an intense cold neutron beam. In this work we analyzed the ²³⁵U targets. We studied several fission fragments and more generally the fission process by using high-resolution γ-ray spectroscopy. At the beginning, we used the standard γ-γ-γ coincidence analysis method. We were able to filter experimental data, identify the well produced γ-rays, and calculate their relative intensities. The problems we have encountered are related to the background. The results obtained with this method were background dependent and thus presented some problems with reproducibility. We therefore developed and tested a new analysis methodology. Its crucial feature is a coincidence gates scanning in three directions which helps to find the most suitable background. The idea was to move from a “spectroscopic” method, which main purpose is finding new transitions and excited states in a nucleus, to a “spectrometric” method, which allows us to obtain more precise γ-ray intensities. We developed a semi-automatic analysis software which facilitates fitting of the chosen γ-ray peak, the contamination and the background. Various γ-ray intensity calculation schemes were derived to take into account different contamination strengths and placements. The results of the analysis with the new technique are reproducible and more reliable. The standard and the new analysis method were compared in the ¹⁴²Ba analysis. In this work, we also compared our experimental results on some nuclei, such as ¹⁰⁰Zr, with the simulation results performed with the FIFRELIN code. It is a Monte-Carlo code which simulates the fission process and the de-excitation of the fission fragments. It uses various models to describe these processes. We were able to test the behavior of different models implemented in FIFRELIN to find the optimal simulation parameter values and to test how well these setups reproduce the experimental results. FIFRELIN was unable to simultaneously reproduce the γ-ray intensities of ¹⁰⁰Zr and the prompt-neutron multiplicity averaged over all fission fragments. However, with modified simulation parameters, FIFRELIN locally provided correct prompt-neutron multiplicity for the fission fragment with the atomic mass A=100 and well reproduced γ-ray intensities of ¹⁰⁰Zr. We also compared our experimental results on ¹⁰⁰Zr coming from the ²³⁵U(n,f) process with the other available experimental data coming from the experiments on ²⁴⁸Cm(sf) and ²⁵²Cf(sf), and another experiment on ²³⁵U(n,f).

Un-doped, Tb3+ as well as Yb3+ doped ZnO nanocrystals with different concentrations of RE3+ (Tb3+, Yb3+) ions were successfully synthesized via sol-gel method to produce rare earth activated zinc oxide nanophosphors. The phosphor powders were produced by drying the precursor gels at 200˚C in ambient air. Based on the X-ray diffraction results, it was found that the pure and RE3+ doped ZnO nanophosphors were highly polycrystalline in nature regardless of the incorporation of Tb3+ or Yb3+ ions. Moreover, the diffraction patterns were all indexed to the ZnO Hexagonal wurtzite structure and belong to P63mc symmetry group. The Raman spectroscopy confirmed the wurtzitic structure of the prepared samples. Elemental mapping conducted on the as prepared samples using Scanning electron microscope (SEM) equipped with energy dispersive X-ray spectrometer (EDX) revealed homogeneous distribution of Zn, O, and RE3+ ions. The high resolution transmission electron microscope (HR-TEM) analyses indicated that the un-doped and RE3+ doped samples were composed of hexagonal homogeneously dispersed particles of high crystallinity with an average size ranging from 4 to 7 nm in diameter, which was in agreement with X-ray diffraction (XRD) analyses. ZnO:Tb3+ PL study showed that among different Tb3+ concentrations, 0.5 mol% Tb3+ doped ZnO nanoparticles showed clear emission from the dopant originating from the 4f-4f intra-ionic transitions of Tb3+ while the broad defects emission was dominating in the 0.15 and 1 mol% Tb3+doped ZnO. Optical band-gap was extrapolated from the Ultraviolet Visible spectroscopy (UV-Vis) absorption spectra using TAUC‟s method and the widening of the optical band-gap for the doped samples as compared to the un-doped sample was observed. The PL study of ZnO:Yb3+ samples was studied using a 325 nm He-Cd laser line. It was observed that the ZnO exciton peak was enhanced as Yb3+ions were incorporated in ZnO matrix. Furthermore, UV-VIS absorption spectroscopic study revealed the widening of the band-gap in Tb3+ doped ZnO and a narrowing in the case of Yb3+ doped ZnO system. X-ray photoelectron spectroscopy demonstrated that the dopant was present in the doped samples and the result was found to be consistent with PL data from which an energy transfer was evidenced. Energy transfer mechanism was evidenced between RE3+ and ZnO nanocrystals and was discussed in detail. / Physics / M.Sc. (Physics)

With the development of new generation synchrotron facilities, the performances of various X-ray spectroscopies have become more advanced. In order to interpret the X-ray spectrum experiments of various novel materials related to transition metal and rare earth elements, new advanced theoretical methods are required. The present thesis incorporates four modus operandi based on the classic multiplet theory to study the core level X-ray spectroscopy of transition metal and rare earth element. The four approaches consist of new methods developed from classic multiplet approach to high level first-principles method assisted multiplet calculation. Some methods are selected from previous researches and some are invented by original researches. These methods are integrated together to form a complete set of multiplet computational methods. This set of multiplet computational methods can perform calculations on various X-ray spectroscopies such as XAS, XPS, XES and RIXS related to the core-level electron. These wide range of spectroscopic methods coupled to different multiplet theory approaches serve as efficient tools to understand the electronic structure of metal sites and their unique contribution to the physical/chemical properties of the materials. The thesis creatively improves the classic multiplet theory on several aspects: (1) the relation between crystal field parameters and local structure factors; (2) the difficulty of processing point group symmetry branching chain in low symmetric structure; (3) the first-principles calculation of semi-empirical parameters. Four modus operandi are presented in this thesis: the first is the classic multiplet theory consisting of the multiplet effect, crystal field effect and charge transfer effect via several semi-empirical parameters as description for these effects. The second level multiplet theoretical approach analyze the crystal field potential matrix in various symmetries according to the point group symmetry branching rules. Then the crystal field effect parameters used in classic multiplet theory are linked analytically to the specific structural factors such as bond length and angles. This approach is a good tool to study the structural distortion from higher to lower order symmetry with analysis of X-ray spectral feature changes in experiment. The third modus operandi adopts large cluster model consisting of point charges at equivalent atoms position to simulate the crystal field effect on the center metal site. This approach handles low order symmetric crystal field with long range effect in multiplet calculation in an easier way than the classic multiplet theory. The fourth modus operandi initially studies the system of interest in first-principles calculation for the electronic wavefunctions. Then the electronic wavefunctions are used to derive the maximally localized Wannier functions at metal/ligand sites. The analysis of these Wannier functions provide a lot of semi-empirical parameters required in the classic multiplet calculation approach in a first-principles way. This modus operandi has substantially resolved the problem of finding the best set of semi-empirical parameters to fit the calculated X-ray spectrum with experimental data. In order to study the core electrons of the light elements (such as C/N/O) around center metal ions, a theoretical calculation method used to study the core electrons' vibrationally-resolved X-ray spectroscopy is also introduced as a complementary research and applied to C1s core ionized XPS calculation as an example. / Med utvecklingen av nya generationens synkrotronanläggningar har prestandan för olika röntgenspektroskopier blivit mer avancerad. För att tolka röntgenspektrumexperiment av olika nya material relaterade till övergångsmetaller och sällsynta jordartsmetaller krävs nya avancerade teoretiska metoder. Denna avhandling inkorporerar fyra metoder baserade på den klassiska multiplettläran för att studera röntgenspektroskopi på kärnenerginivån för övergångsmetaller och sällsynta jordartsmetaller. De fyra metoderna består av nya metoder som utvecklats från den klassiska multiplettläran till multiplettberäkning med hjälp av högnivå-först-principer-metoder. Vissa metoder har valts från tidigare forskning och några har uppfunnits genom originalforskning. Dessa metoder integreras för att bilda en komplett uppsättning av multiplettberäkningsmetoder. Denna uppsättning av multiplettberäkningsmetoder kan utföra beräkningar av olika röntgenspektroskopier som XAS, XPS, XES och RIXS relaterade till elektroner på kärnenerginivån. Denna breda spektrum av spektroskopiska metoder som kopplas till olika multipletteteoretiska tillvägagångssätt fungerar som effektiva verktyg för att förstå den elektroniska strukturen hos metalliska platser och deras unika bidrag till materialets fysikaliska/kemiska egenskaper. Avhandlingen förbättrar på ett kreativt sätt den klassiska multiplettläran på flera områden: (1) förhållandet mellan kristallfältparametrar och lokala strukturfaktorer, (2) svårigheten med att hantera förgreningskedjor i punktgruppsymmetri för strukturer med låg symmetri, (3) först-principer-beräkning av semi-empiriska parametrar. Fyra metoder presenteras i denna avhandling: den första är den klassiska multiplettläran som omfattar multiplett-effekten, kristallfältseffekten och laddningsöverföringseffekten genom flera semi-empiriska parametrar som beskriver dessa effekter. Den andra multiplett-teoretiska tillvägagångssättet analyserar kristallfältspotensialmatrisen i olika symmetrier enligt reglerna för punktgruppsymmetri. Därefter kopplas de kristallfältseffektparametrar som används i den klassiska multiplettläran analytiskt till specifika strukturella faktorer som bindningslängd och vinklar. Detta tillvägagångssätt är ett bra verktyg för att studera strukturell distorsion från högre till lägre ordningssymmetri med analys av förändringar i röntgenspektrala funktionsändringar i experiment. Det tredje tillvägagångssättet använder en stor klustermetod som består av punktladdningar på ekvivalenta atompositioner för att simulera kristallfältsinverkan på metallcentralen. Detta tillvägagångssätt hanterar kristallfält med låg symmetri och lång räckvidd i multiplettberäkningar på ett enklare sätt än den klassiska multiplettläran. Det fjärde tillvägagångssättet studerar initialt det intressanta systemet med först-principer-beräkningar av elektronvågfunktioner. Därefter används dessa elektronvågfunktioner för att härleda maximalt lokaliserade Wannier-funktioner vid metall-/ligandpositioner. Analysen av dessa Wannier-funktioner ger många av de semi-empiriska parametrar som krävs i den klassiska multiplettberäkningsmetoden på ett först-principer-sätt. Detta tillvägagångssätt har i stor utsträckning löst problemet med att hitta den bästa uppsättningen semi-empiriska parametrar för att anpassa de beräknade röntgenspektrumen med experimentella data. För att studera de lättas elektroner (som C/N/O) runt centrala metalljoner introduceras även en teoretisk beräkningsmetod för att studera röntgenspektrum med vibrationell upplösning för kärnelektroner som ett kompletterande forskningsområde och tillämpas på beräkningar av C1s-kärnenerginivåns XPS som ett exempel. / <p>QC 2023-05-23</p>

Durch die Kopplung von Szintillationskristallen an Lichtwellenleiter könnten robuste Messgeräte für die spektroskopitsche Messung von Strahlungsfeldgrößen in Bohrlöchern in Betonstrukturen beim Rückbau von Kernkraftwerken realisiert werden. In dieser Arbeit wurden zwei Prototypen solcher Messgeräte entwickelt, wobei ein auf einem Gadolinium-Aluminium-Gallium-Granat-Szintillationskristall basierendes Messsystem mit einem Kunststofflichtwellenleiter mit hohem Durchmesser aufgrund seiner hohen Zählrate bevorzugt wurde. Mit diesem Messystem konnten spektroskopische Messungen von Gammastrahlung durchgeführt werden. Weiterhin konnte gezeigt werden, dass Kontaminationen einer bestimmten Aktivität bis in einen Abstand von mehreren Zentimetern von der Messsonde im Beton nachweisbar sind. Ein Schätzwert der minimale Messzeit zur Erkennung einer nachweisbaren Kontamination konnte bestimmt werden. Eine hinreichend große, gemessene Ereigniszahl ermöglicht zusätzlich die Bestimmung des Abstands einer radioaktiven, punktförmigen Kontamination eines bekannten Nuklids. Für ein bekanntes Nuklid konnte weiterhin aus der Zählrate ein Schätzwert für die Energiedosis am Ort der Messsonde mithilfe von Referenzmessungen der Dosis mittels Berylliumoxid-Detektoren bestimmt werden.:Inhaltsverzeichnis Abbildungsverzeichnis vii Tabellenverzeichnis ix 1 Einleitung 1 2 Physikalische Grundlagen 3 2.1 Radioaktiver Zerfall 3 2.2 Gröÿen des Strahlungsfelds 3 2.3 Wechselwirkungen von Photonen mit Materie 5 2.4 Lichtentstehung in anorganischen Szintillatoren 8 2.5 Lichtmessung 10 2.6 Pulshöhenverteilungen von Szintillationsdetektoren 12 2.7 Ein ussfaktoren der Lichtausbeute 14 3 Material und Methoden 16 3.1 Aufbau LSO-Sonde und Messungen mit radioaktiven Quellen 16 3.2 Aufbau Lichtkopplung mittels Linse 18 3.3 Aufbau und Versuchsablauf Quarzglaskopplungen 20 3.4 Aufbau GAGG-Sonde 21 3.5 Aufbau des Betonphantoms 24 3.5.1 Dichtebestimmung des Betonphantoms 24 3.6 Messablauf Tiefenkurven in Betonphantom 27 3.7 Datenanalyse mittels Kolmogorv-Smirnov-Test 27 4 Ergebnisse 29 4.1 Spektroskopische Eigenschaften LSO-Sonde 29 4.2 Winkelverteilung austretender Photonen aus Szintillationskristall 33 4.3 Quarzglaskopplung 36 4.4 Spektroskopische Eigenschaften GAGG-Sonde 43 4.5 Vergleich GAGG- und LSO-Sonde 47 4.6 Abstandsabhängigkeit der Zählrate 50 4.7 Abschätzung der maximalen Abschirmdicke von Beton für Kontaminationserkennung 53 4.8 Abschätzung der minimalen Messzeit zur Kontaminationserkennung 56 4.9 Abschirmungsdickenbestimmung mittels Abschirmungsparameter 57 4.10 Bestimmung der Dosis 62 5 Diskussion 64 6 Zusammenfassung 67 / A robust measuring system for spectroscopic measurementes of gamma-ray radiation in boreholes in concrete structures can be built by coupling of a scintillation crystal to a light guide. Two prototypes of such measuring systems are developed one based on a Gadolinium-Aluminium-Gallium-Garnet scintillation crystal with a plastic optical fiber with a high diameter is preferred due to the higher count rate. Spectroscopic measurements of gamma-ray radiation with this measuring system can be performed. It can be shown that contamination of a specific activity can be detected even if they are located in concrete in a distance of several centimeters from the radiation sensor. for the minimal measurement time of 38 s An estimated value to detect a traceable contamination could be determined. If a high number of events can be detected, even the distance between a point like radioaktive source of a known nuclide and the radiation sensor can be determined. An estimated value for the applied dose at the place of the radiation sensor could be determined for a known nuclide with the help of the count rate. Therefore, reference measurements of dose with berylliumoxide detectors were performed.:Inhaltsverzeichnis Abbildungsverzeichnis vii Tabellenverzeichnis ix 1 Einleitung 1 2 Physikalische Grundlagen 3 2.1 Radioaktiver Zerfall 3 2.2 Gröÿen des Strahlungsfelds 3 2.3 Wechselwirkungen von Photonen mit Materie 5 2.4 Lichtentstehung in anorganischen Szintillatoren 8 2.5 Lichtmessung 10 2.6 Pulshöhenverteilungen von Szintillationsdetektoren 12 2.7 Ein ussfaktoren der Lichtausbeute 14 3 Material und Methoden 16 3.1 Aufbau LSO-Sonde und Messungen mit radioaktiven Quellen 16 3.2 Aufbau Lichtkopplung mittels Linse 18 3.3 Aufbau und Versuchsablauf Quarzglaskopplungen 20 3.4 Aufbau GAGG-Sonde 21 3.5 Aufbau des Betonphantoms 24 3.5.1 Dichtebestimmung des Betonphantoms 24 3.6 Messablauf Tiefenkurven in Betonphantom 27 3.7 Datenanalyse mittels Kolmogorv-Smirnov-Test 27 4 Ergebnisse 29 4.1 Spektroskopische Eigenschaften LSO-Sonde 29 4.2 Winkelverteilung austretender Photonen aus Szintillationskristall 33 4.3 Quarzglaskopplung 36 4.4 Spektroskopische Eigenschaften GAGG-Sonde 43 4.5 Vergleich GAGG- und LSO-Sonde 47 4.6 Abstandsabhängigkeit der Zählrate 50 4.7 Abschätzung der maximalen Abschirmdicke von Beton für Kontaminationserkennung 53 4.8 Abschätzung der minimalen Messzeit zur Kontaminationserkennung 56 4.9 Abschirmungsdickenbestimmung mittels Abschirmungsparameter 57 4.10 Bestimmung der Dosis 62 5 Diskussion 64 6 Zusammenfassung 67

No description available.

In strongly correlated electron systems the intricate interplay between electronic correlation effects and the tendency to form bands leads to a wealth of fascinating physical phenomena. The theoretical description of such systems is extremely complex and cannot be tackled exactly, so that ingenious modelling based on approximations must be utilized. Experiments are of utmost importance in this regard, since they provide a way to test and verify models, or to help devise better ones. This Dissertation deals with strongly correlated uranium intermetallic systems. The interesting phases they can adopt include heavy fermion behaviour, unconventional superconductivity, hidden and multipolar order, and exotic induced magnetism. Here the hybridization between the 5f states and the conduction electrons drives the physics. The description of the 5f states is therefore of utmost importance. However, since there is no clear hierarchy of interactions like Coulomb repulsion, spin-orbit coupling, hopping and crystal-field, the modelling is difficult. This is in strong contrast to the more spatially localized 4f states of, e.g., cerium compounds. It is far from clear how to quantitatively describe the electronic structure of uranium intermetallics and whether, for example, an itinerant band approach or an impurity-type model, taking local degrees of freedom explicitly into account, would be a better starting point. In intermetallics, the situation is aggravated by the fact that the modelling lacks important pieces of information. This is not least due to the fact that understanding the formal valence, the filling of the 5f shell, and the relevant symmetries of the $5f$ electrons are experimentally demanding tasks. This Dissertation, therefore, aims at developing new methods and Ans\'atze in this direction. We use x-ray spectroscopy to investigate the electronic structure, and in particular element-specific Inelastic X-ray Scattering (IXS); resonant (RIXS) at the U M(5) edge and non-resonant (NIXS) at the U O(4,5) edge. Both methods are innovative. For the first time, valence band RIXS measurements with sufficient resolution (150 meV) can be carried out at the U M(5) edge to measure ff excitations in intermetallic uranium compounds. Their existence, if present, provides information about the formal valence or main atomic configuration that determines the symmetry. The orientation dependence of the mutipolar excitations in NIXS (with restrictions also in RIXS), in turn, provides information about the orbital occupation. Atomic full-multiplet calculations are indispensable here. In addition, photoelectron spectroscopy (PES) is applied, both in the soft as well as in the hard x-ray regime (HAXPES), to investigate the hybridization and localization of the 5f electrons. The energy dependence of the cross-sections allows to determine the orbital contributions in the valence band, so that parameters like, e.g., the double-counting correction for the LDA+DMFT calculations, performed by Prof. A. Hariki from the Osaka Metropolitan University, can be determined from tuning the calculations to the experimental data. This combination of PES and DFT+DMFT provides a reliable new quantitative insight into the number of electrons in the 5f shell and their degree of delocalization. We consider UGa(2) and UB(2), respectively, as benchmark localized and itinerant systems and investigate them with IXS and PES. UGa(2) is a high-moment ferromagnet, with U-U distances above the Hill limit, while UB(2) is paramagnetic and clearly below the Hill limit. We observe sharp multiplet excitations of the 5f2 configuration in the IXS spectra of UGa(2), but none in the spectra of UB(2). The comparison of the spectra with full-multiplet calculations shows that in UGa(2) the U 5f2 configuration dominates and, from the orientation dependence (RIXS and NIXS), the crystal-field ground state can be determined. We show that the magnetism of this compound is of the induced type. The cross-section based analysis of the valence band PES data with the LDA+DMFT approach shows that the filling of the 5f shell is similar in both compounds, but that the distribution among different configurations is considerably wider in UB(2). Also the time-dependent charge correlation functions of UGa(2) and UB(2) show a larger itinerancy in the latter compound. The peculiarity and novelty about this combined study is that a reliable quantitative description of the electronic structure is achieved. This allows, for the first time, an accurate estimation of the 5f occupation and a quantitative description of the U\ 4f core-level PES spectra. This study paves the way to a systematic classification of uranium intermetallics. We further investigate the substitution series URu(2-x)Fe(x)Si(2) with PES. The systematic study of isostructural and/or isoelectronic series of compounds is crucial in unveiling the origin of their physical properties. URu(2)Si(2) exhibits hidden-order as well as superconductivity, and becomes antiferromagnetic upon Fe doping. Fe substitution seemingly involves the application of chemical pressure to the system. We measure the U 4f PES core-level of the URu(2-x)Fe(x)Si(2) substitution series and observe a non-monotonic shift of spectral weight. We argue that, besides chemical pressure, the Fe density of states at the Fermi level also plays a central role and we propose and extended Doniach diagram where the two effects compete. We also measure NIXS, confirming that the ground state symmetry is a singlet or quasi-doublet of the 5f2 configuration. The magnetic properties must then be understood, as in UGa(2), in terms of induced magnetism. We extend our study of the UT(2)Si(2) compounds to the case where T = Os, Ir, Pt and Au, i.e. 5d transition metals. Although the T= 3d and 4d transition metal systems have been extensively investigated, the T = 5d compounds lack systematic studies. The comparison of the NIXS spectra with multiplet calculations shows that also here the 5f2 dominates, only for T= Au it is not so clear. The absence of a strong directional dependence impairs the identification of the ground state symmetry. Valence band hard x-ray PES allows to probe the transition metal 5d states directly. U 4f core-level hard x-ray PES gives a qualitative indication of the filling of the 5f shell across the series. We then focus on hexagonal UNi(2)Al(3) and apply NIXS. Like isoelectronic and isostructural UPd(2)Al(3), it is a prototypical U heavy-fermion compound, showing antiferromagnetic order and unconventional superconductivity. We observe a strong directional dependence of the NIXS spectra at low temperatures. The possible ground-state symmetries of the 5f2 configuration that fit the NIXS data are in contradiction to previous proposals from fits of the static magnetic susceptibility. We put forward a new crystal-field model that describes the high temperature magnetic susceptibility and the NIXS data at low temperatures, and that explains the magnetism.

Zwischen 10 und 1000 s nach dem Urknall bildeten sich während der Big Bang Nukleosynthese (BBN) die ersten leichten Elemente aus Protonen und Neutronen. Die primordialen Häufigkeiten dieser Elemente hingen von denWirkungsquerschnitten der beteiligten Kernreaktionen ab. Vergleiche zwischen den Ergebnissen nuklearer Netzwerkrechnungen mit astronomischen Beobachtungen bieten eine einzigartige Möglichkeit, etwas über das Universum zu dieser Zeit zu erfahren. Da es für die p(n,g)d-Reaktion, die eine Schlüsselreaktion der BBN ist, kaum Messungen im relevanten Energiebereich gibt, beruht deren Reaktionsrate in Netzwerkrechnungen auf theoretischen Berechnungen. Darin fließen auch experimentelle Daten der Nukleon-Nukleon-Streuung, des Einfangquerschnitts für thermische Neutronen sowie (nach Anwendung des Prinzips des detaillierten Gleichgewichts) der d(g,n)p-Reaktion mit ein. Diese Reaktion, die Photodissoziation des Deuterons, ist bei BBN-Energien (Tcm = 20–200 keV) ebenfalls kaum vermessen. Die großen experimentelle Unsicherheiten machen Vergleiche mit den präzisen theoretischen Berechnungen schwierig. In den letzten Jahren wurde die d(g,n)p-Reaktion und insbesondere der M1-Anteil des Wirkungsquerschnitts mit quasi-monoenergetischen g-Strahlen aus Laser-Compton-Streuung oder durch Elektrodesintegration untersucht. Üblicherweise verwendete man für Messungen des d(g,n)p-Wirkungsquerschnitts entweder die auf wenige diskrete Energien beschränkte Strahlung des g-Zerfalls oder Bremsstrahlung, für die aber eine genaue Photonenflussbestimmung sowie der Nachweis von einem der Reaktionsprodukte und dessen Energie nötig ist. Da diese Energie im Bereich der BBN relativ gering ist, gab es bisher noch keine absoluten Messung des d(g,n)p-Wirkungsquerschnitts bei Tcm < 5 MeV mit Bremsstrahlung. Das Ziel dieser Dissertation ist eine solche Messung mit einer Unsicherheit von 5 % im für die BBN relevanten Energiebereich und darüber hinaus bis Tcm ~ 2,5 MeV unter Verwendung gepulster Bremsstrahlung an der Strahlungsquelle ELBE. Dieser supraleitende Elektronenbeschleuniger befindet sich am Helmholtz-Zentrum Dresden-Rossendorf und stellte einen Elektronenstrahl hoher Intensität bereit. Die kinetische Elektronenenergie von 5 MeV wurde mit einem Browne-Buechner-Spektrometer präzise gemessen. Die Energieverteilung der in einer Niob-Folie erzeugten Bremsstrahlungsphotonen wurde berechnet. Die Photonenflussbestimmung nutzte die Kernresonanzstreuung an 27Al, das sich mit deuteriertem Polyethylen in einem mehrschichtigen Target befand. Die 27Al-Abregungen wurden mit abgeschirmten, hochreinen Germanium-Detektoren nachgewiesen, deren Effektivität mit GEANT4 simuliert und durch Quellmessungen normiert wurde. Die Messung der Energie der Neutronen aus der d(g,n)p-Reaktion erfolgte mittels deren Flugzeit in Plastikszintillatoren, die an zwei Seiten von Photoelektronenvervielfachern mit hoher Verstärkung ausgelesen wurden. Die Nachweiseffektivität dieser Detektoren wurde in einem eigenen Experiment in den Referenz-Neutronenfeldern der PTB Braunschweig kalibriert. Die Nachweisschwelle lag bei etwa 10 keV kinetischer Neutronenenergie.Wegen der guten Zeitauflösung der Neutronendetektoren und des ELBE-Beschleunigers genügte eine Flugstrecke von nur 1 m. Die Energieauflösung betrug im d(g,n)p-Experiment 1–2 %. Leider gingen viele Neutronen bereits durch Streuung in dem großen Target verloren oder sie wurden erst durch Teile des kompakten Experimentaufbaus in die Detektoren gestreut. Beide Effekte wurden mit Hilfe von FLUKA simuliert um einen Korrekturfaktor zu bestimmen, der aber bei niedrigen Energien relativ groß war. Der d(g,n)p-Wirkungsquerschnitts wurde daher nur im Bereich 0.7 MeV < Tcm < 2.5 MeV bestimmt. Die Ergebnisse stimmen mit anderen Messungen, Daten-Evaluierungen sowie theoretischen Rechnungen überein. Die Gesamtunsicherheit beträgt circa 6.5 % und kommt zu fast gleichen Teilen von den statistischen und systematischen Unsicherheiten. Die statistische Unsicherheit könnte durch eine längere FLUKA Simulation noch von 3–5 % auf 1 % verringert werden. Die systematische Unsicherheit von 4.5 % ist vorrangig auf die Photonenflussbestimmung, die Neutronen-Nachweiseffektivität und die Target-Zusammensetzung zurückzuführen.

La structure sous-jacente dans la zone A~100, N~60 a été étudié intensivement et extensivement, principalement par décroissance β et spectroscopie γ suite à des réactions de fission. Autour de N~60, en ajoutant juste quelques neutrons, protons un changement de forme rapide des états fondamentaux se produit, allant de sphérique à bien déformé. La coexistence de forme observée dans les noyaux de Sr et Zr est supposée avoir lieu dans toute la région. Les mécanismes impliqués dans l'apparition de la déformation n'étaient pas clairement identifiés. L'interaction entre les orbitales de Nilsson montantes et descendante est évoqué comme l'une des principales raisons du changement de forme. Cependant, une identification claire des orbitales proton et neutron en jeu était nécessaire. A cet effet, l'étude des isotopes ⁹³′⁹⁵′⁹⁷′⁹⁹Rb riches en neutrons a été réalisé excitation Coulombienne au CERN (ISOLDE) en utilisant le post-accélérateur REX-ISOLDE et le dispositif Miniball. Les structures excitées encore inconnues des isotopes ⁹⁷′⁹⁹Rb ont été peuplées et observées. Les coïncidences de transitions γ des états de basse énergie ont été observées et leur corrélations ont permis la construction de schémas de niveaux. Les probabilités de transitions associées ont été extraites grâce code GOSIA. Les éléments de matrice de l'opérateur électromagnétique observées constituent de nouveaux apports afin d'effectuer de nouveaux calculs théoriques permettant de statuer sur les orbitales impliquées. La sensibilité des expériences de ce type peut être accrue en utilisant des faisceaux radioactifs d'ions dont le spin nucléaire est polarisé. La technique de polarisation des feuilles orientées (TFT) fut étudiée dans ce but au CERN. Un nouveau polariseur TFT et un dispositif β-NMR ont être créés et installés après REX-ISOLDE. La connaissance du processus de polarisation associé à la technique reste incomplète à ce jour et de plus amples études sont nécessaires. Des tests préliminaires prometteurs ont été effectués sur le noyau de ⁸Li afin de déterminer le potentiel du dispositif actuel.

Nanotechnology offers a great potential do design fertilizers with unique properties capable to boost the plant productivity. However, the nanoparticles environmental fate and their toxic responses still need to be deeply investigated to their safe use. This study aims to investigate the effect of copper oxide (nCuO) and magnetite nanoparticles (nFe3O4) on the germination and seedling development of Phaseolus vulgaris L. Seeds were treated in nanoparticles dispersions in a wide range of concentrations (1, 10, 100 and 1 000 mg L-1) and incubated in a germination chamber during 5 days. Different sized nCuO (25, 40 and <80 nm) and polyethylene glycol (PEG) coated nFe3O4 were evaluated. Although both nCuO and nFe3O4 treatments did not affected the germination rate, seedling weight gain was promoted by 40 nm CuO at 100 mg Cu L-1 and inhibited by 1 000 mg Cu L-1 of 25 nm CuO and positive control (CuSO4). Among the tested nCuO, the higher chemical reactivity was found for the 25 nm CuO, and this may partially explain the observed deleterious effects. Seeds treated in nFe3O4-PEG at 1 000 mg Fe L-1 increased radicle elongation compared to the negative control (water), while Fe2+/Fe3+ (aq) (positive control) and bare nFe3O4 at 1 000 mg Fe L-1 treatments reduced the radicle of the seedlings. The growth promoted by the PEG-coated nanoparticles can be justified by the higher water uptake induced by the PEG, and also by its lower chemical reactivity compared to the bare nanoparticles. This was reinforced by enzymatic assays since nFe3O4-PEG treatment was also the least harmful to the alpha-amylase activity. X-ray fluorescence spectroscopy (XRF) showed that most of the Cu and Fe incorporated by the seeds remained in the seed coat, specially in the hilum region, and X-ray tomography indicated that Fe3O4-PEG penetrated in this structure. X-ray absorption spectroscopy (XAS) unraveled that the Cu and Fe chemical environment of the nCuO and nFe3O4-PEG treated seeds persisted mostly in its primitive form. These results contribute to the understanding of how nCuO, nFe3O4 and nFe3O4-PEG interact with common bean seeds and seedlings and highlights its potential use in seed priming / A nanotecnologia oferece um grande potencial para o desenvolvimento de fertilizantes com propriedades únicas, capazes de impulsionar a produtividade das plantas. Contudo, o destino ambiental e os efeitos tóxicos das nanopartículas ainda necessitam ser profundamente investigados para o seu uso seguro. Este estudo visa investigar o efeito das nanopartículas de óxido de cobre (nCuO) e magnetita (nFe3O4) na germinação e desenvolvimento das plântulas de Phaseolus vulgaris L. As sementes foram tratadas em dispersões de nanopartículas em diversas concentrações (1, 10, 100 and 1 000 mg L-1) e incubadas em uma câmara de germinação durante 5 dias. Diferentes tamanhos de nCuO (25, 40 e <80 nm) e nFe3O4 recoberta com polietileno glicol (PEG) e foram avaliados. Embora ambos tratamentos de nCuO e nFe3O4 não afetaram a taxa de germinação, o ganho de massa das plântulas foi promovido pela nCuO de 40 nm à 100 mg Cu L-1 e inibido pelos tratamentos de nCuO de 25 nm e controle positivo (CuSO4) à 1 000 mg Cu L-1. Dentre as nCuO testadas, a maior reatividade química foi encontrada para a nCuO de 25 nm, e isso pode explicar parcialmente os efeitos deletérios desta nanopartícula. Sementes tratadas com nFe3O4-PEG à 1 000 mg Fe L-1 aumentaram o alongamento das radículas em comparação ao controle negativo (água), enquanto que os tratamentos Fe2+/Fe3+ (aq) (controle positivo) e nFe3O4 sem recobrimento à 1 000 mg Fe L-1 reduziram as radículas das plântulas. O crescimento promovido pelas nanopartículas recobertas com PEG pode ser justificado pela maior absorção de água induzido pelo PEG, e também pela sua baixa reatividade química comparada às nanopartículas sem recobrimento. Isso foi reforçado por ensaios enzimáticos uma vez que o tratamento de nFe3O4-PEG foi também o menos prejudicial à atividade da alfa-amilase. A espectroscopia de fluorescência de raios-X (XRF) mostrou que a maior parte do Cu e do Fe incorporados pelas sementes permaneceu no tegumento, especialmente na região do hilo, e a tomografia de raios-X indicou que nFe3O4-PEG penetrou nesta estrutura. A espectroscopia de absorção de raios-X (XAS) revelou que o ambiente químico do Cu e do Fe das sementes tratadas com nCuO e nFe3O4-PEG persistiram majoritariamente em sua forma primitiva. Estes resultados contribuem para o entendimento de como nCuO, nFe3O4 e nFe3O4-PEG interagem com sementes de feijão e destaca seu potencial uso no tratamento de sementes