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This thesis was dedicated to the studies of the electronic and chemical properties of liquids and solutions using soft x-ray spectroscopies. The used photon-in-photon-out methods namely x-ray absorption spectroscopy (XAS), x-ray emission spectroscopy (XES), and resonant inelastic x-ray scattering (RIXS) appeared to be an excellent choice for these studies. In the framework of this thesis, the necessary experimental setup for using the above mentioned experimental techniques on liquids was developed. Hereby, a new flow-through liquid cell was introduced which simplifies the studies of liquids and solutions. The cell design is very flexible and thus can be modified for gases and liquid/solid interfaces. With this cell it is possible to study the samples under well-controlled conditions (temperature and flow rate). The novel flow-through liquid cell is part of the new SALSA synchrotron endstation including an electron analyzer and a novel high-resolution, high-transmission soft x-ray spectrometer. The latter makes it possible to measure two-dimensional RIXS maps in a very short time, which include the full excitation and emission information in one plot. Making use of the new instrumentation, a variety of different liquids and solutions were investigated. As first system, aqueous solutions of sodium hydroxide (NaOH) and sodium deuteroxide (NaOD) were investigated. In the XAS as well as in the XES spectra a pronounced concentration dependence was found. At non-resonant energies, the spectra are dominated by the solvent and thus look similar to water. Making use of the pre-pre-edge in the absorption spectra which can exclusively be attributed to OH- / OD- it was possible to extract the resonant emission spectra of the ions which show an indication for proton dynamics during the core-hole lifetime. For the solid state NaOH XES spectra it was possible to reveal a high energetic shoulder and a low energetic shoulder at the high energy emission feature. These shoulders can be assigned to self-dissociation processes where OH- forms O2- ions and H2O. The study of NaOH was also of interest for the studies of the amino acids, which were in the focus of the next part, since the pH-values of the respective solutions were controlled by NaOH. In the next part of this thesis, amino acid solutions were investigated. Amino acids are the building blocks of peptides and proteins and thus important for life science. The investigated representatives were glycine, the simplest amino acid, and lysine, an amino acid with two amine groups. Both amino acids react on pH-value changes at the amine group where the local environment at the nitrogen atom changes (NH2 ↔ NH3+). A strong change of the spectra induced by this protonation/deprotonation could be found. Furthermore, for low pH-values (protonated amine groups) the amine groups are influenced by strong proton dynamics. First DFT calculations confirm the dissociation model of the amino acids. Qualitatively the high energy peak in the N K XES spectra can be attributed to the deprotonated amine group and the low energy area for the protonated amine group. Besides amino acids, alcohols and acids are important in biological processes. Therefore, the smallest alcohol (methanol) and the smallest carboxylic acid (acetic acid) were under investigation. For the liquid methanol XES spectra a very good agreement with DFT calculations of gas phase methanol could be found. This observation suggests that the influence of the environment (hydrogen bonding) on the spectra is small. The achieved spectra are in good agreement with DFT calculations found in literature. It was possible to selectively excite the two non-equivalent oxygen atoms in acetic acid and to reveal the carboxyl specific C K XES. The carbon XAS spectra showed strong differences compared to gas phase measurements which might be a hint for the influence of the hydrogen bond network. The investigation of the electronic and chemical properties of liquids and solutions is a very young field of research and the results presented in this thesis show that it is a very interesting topic. The presented results can be seen as the fundamental frame work for all following studies. With the understanding of basic, i.e., simple, systems as shown in this work it will be possible to understand complex biological systems in their native environment, e.g., peptides and proteins, which are the building blocks of life.
In this work, high-energy observables arising during different phases of SN explosions are studied with respect to their potential for allowing conclusions on suggested explosion scenarios and physical mechanisms that are thought to influence the evolution of SNe in a major way. The focus on selected observables at keV and MeV energies is motivated by the appearance of large degeneracies that can even be found for disparate scenarios in many wavelength regimes. Since the discussed emission in the high-energy regime is directly linked to nuclear processes being usually very distinct for different suggested physical models, the signatures at keV and MeV energies allow for meaningful comparisons of simulations with observations.
Hard X-ray Properties of Relativistically Beamed Jets from Radio- and Gamma-Ray-Bright Blazars
(2022)
In this work I characterize the hard X-ray properties of blazars, active galactic nuclei with highly beamed emission, which are notoriously hard to detect in this energy range. I employ pre-defined samples of beamed AGN: the radio-selected MOJAVE and TANAMI samples, as well as the most recent gamma-ray-selected Fermi/LAT 4LAC catalog. The hard X-ray data is extracted from the 105-month all-sky survey maps of the Swift/BAT (Burst Alert Telescope) in the energy band of 20 keV to 100 keV. A great majority of both the MOJAVE and TANAMI samples are significantly detected, with signal-to noise ratios of the sources often just below the X-ray catalog signal thresholds. All blazar sub-types (FSRQs, BL Lacs) and radio galaxies show characteristic ranges of X-ray flux, luminosity, and photon index. Their properties are correlated with the corresponding SED's shape / peak frequency. The LogN-LogS distributions of the samples show a scarcity of blazars in the middle and lower X-ray flux range, indicating differing evolutionary paths between radio and X-ray emission, which is also suggested by the corresponding luminosity functions. Compared to the radio samples, the 4LAC sources are on average significantly less bright in the BAT band since this range often coincides with the spectral gap region between the two big SED emission bumps. Also, the spectral shapes differ notably, especially for the sub-type of BL Lacs. Using the parameter space of X-ray and gamma-ray photon indices, 35 blazar candidate sources can be assigned to either the FSRQ or BL Lac type with high certainty. The reason why many blazars are weak in this energy band can be traced back to a number of factors: the selection bias of the initial sample, differential evolution of the X-rays and the wavelengths in which the sample is defined, and the limited sensitivity of the observing instruments.