Über die Stärke mehrelektronischer Resonanzen bei der Photorekombination und -ionisation

Die Beiträge trielektronischer Prozesse zur resonanten Rekombination hochgeladener Ionen sowie der zur Rekombination zeitumgekehrte Prozess der resonanten Photoionisation wurden mit hoher Auflösung experimentell untersucht. Bei den bisher wenig beachteten Anregungskanälen der resonanten Elektron-Ion-Rekombination einer höheren Ordnung als der dielektronischen Rekombination (DR) wurden überraschend hohe Resonanzstärken gefunden, die den Zustand astrophysikalischer und erdgebundener Plasmen deutlich beeinflussen können. Die systematische Untersuchung dieser zwischen zwei Hauptschalen wirkenden Trielektronischen Rekombination (TR) an L-Schalen Ionen von Argon und Eisen – zwei astrophysikalisch bedeutende Elemente – ermöglichte die Aufstellung entsprechender Skalierungsregeln in Abhängigkeit von Z. Diesen folgend nimmt die Bedeutung der TR für niedrige Z stark zu, so dass die TR den zugehörigen dielektronischen Prozess erster Ordnung (DR) an Stärke übertreffen kann. Das physikalische Bild dieser Vorgänge wurde weiter vervollständigt durch Untersuchungen des zeitumgekehrten Prozesses, nämlich der Photoionisation von Natriumartigem Eisen. Die erstmals gleichzeitig detektierte radiative Relaxation photoangeregter Zustände durch weiche Röntgenstrahlung führte zu einer Bestimmung absoluter Resonanzenergien einer wichtigen Gruppe von in der astrophysikalischen Spektroskopie bisher unaufgelösten Übergängen. Der Vergleich mit eigenen Configuration Interaction-Rechnungen ermöglichte eine detaillierte Analyse der Einflüsse von Elektronen-Korrelation und Konfigurationsmischungen auf beide dynamischen Prozesse und zeigte unerwartet hohe Einflüsse der Breit-Wechselwirkung bereits bei Ionen mittlerer Kernladung

Streptomyces polyketides mediate bacteria–fungi interactions across soil environments

Although the interaction between prokaryotic and eukaryotic microorganisms is crucial for the functioning of ecosystems, information about the processes driving microbial interactions within communities remains scarce. Here we show that arginine-derived polyketides (arginoketides) produced by Streptomyces species mediate cross-kingdom microbial interactions with fungi of the genera Aspergillus and Penicillium, and trigger the production of natural products. Arginoketides can be cyclic or linear, and a prominent example is azalomycin F produced by Streptomyces iranensis, which induces the cryptic orsellinic acid gene cluster in Aspergillus nidulans. Bacteria that synthesize arginoketides and fungi that decode and respond to this signal were co-isolated from the same soil sample. Genome analyses and a literature search indicate that arginoketide producers are found worldwide. Because, in addition to their direct impact, arginoketides induce a secondary wave of fungal natural products, they probably contribute to the wider structure and functioning of entire soil microbial communities

Energy Storage as Part of a Secure Energy Supply

The current energy system is subject to a fundamental transformation: A system that is oriented towards a constant energy supply by means of fossil fuels is now expected to integrate increasing amounts of renewable energy to achieve overall a more sustainable energy supply. The challenges arising from this paradigm shift are currently most obvious in the area of electric power supply. However, it affects all areas of the energy system, albeit with different results. Within the energy system, various independent grids fulfill the function of transporting and spatially distributing energy or energy carriers, and the demand-oriented supply ensures that energy demands are met at all times. However, renewable energy sources generally supply their energy independently from any specific energy demand. Their contribution to the overall energy system is expected to increase significantly. Energy storage technologies are one option for temporal matching of energy supply and demand. Energy storage systems have the ability to take up a certain amount of energy, store it in a storage medium for a suitable period of time, and release it in a controlled manner after a certain time delay. Energy storage systems can also be constructed as process chains by combining unit operations, each of which cover different aspects of these functions. Large-scale mechanical storage of electric power is currently almost exclusively achieved by pumped-storage hydroelectric power stations. These systems may be supplemented in the future by compressed-air energy storage and possibly air separation plants. In the area of electrochemical storage, various technologies are currently in various stages of research, development, and demonstration of their suitability for large-scale electrical energy storage. Thermal energy storage technologies are based on the storage of sensible heat, exploitation of phase transitions, adsorption/desorption processes, and chemical reactions. The latter offer the possibility of permanent and loss-free storage of heat. The storage of energy in chemical bonds involves compounds that can act as energy carriers or as chemical feedstocks. Thus, they are in direct economic competition with established (fossil fuel) supply routes. The key technology here – now and for the foreseeable future – is the electrolysis of water to produce hydrogen and oxygen. Hydrogen can be transformed by various processes into other energy carriers, which can be exploited in different sectors of the energy system and/or as raw materials for energy-intensive industrial processes. Some functions of energy storage systems can be taken over by industrial processes. Within the overall energy system, chemical energy storage technologies open up opportunities to link and interweave the various energy streams and sectors. Chemical energy storage not only offers means for greater integration of renewable energy outside the electric power sector, it also creates new opportunities for increased flexibility, novel synergies, and additional optimization. Several examples of specific energy utilization are discussed and evaluated with respect to energy storage applications. The article describes various technologies for energy storage and their potential applications in the context of Germany’s Energiewende, i.e. the transition towards a more sustainable energy system. Therefore, the existing legal framework defines some of the discussions and findings within the article, specifically the compensation for renewable electricity providers defined by the German Renewable Energy Sources Act, which is under constant reformation. While the article is written from a German perspective, the authors hope this article will be of general interest for anyone working in the areas of energy systems or energy technology

Strong higher-order resonant contributions to x-ray line polarization in hot plasmas

We studied angular distributions of x rays emitted in resonant recombination of highly charged iron and krypton ions, resolving dielectronic, trielectronic, and quadruelectronic channels. A tunable electron beam drove these processes, inducing x rays registered by two detectors mounted along and perpendicular to the beam axis. The measured emission asymmetries comprehensively benchmarked full-order atomic calculations. We conclude that accurate polarization diagnostics of hot plasmas can only be obtained under the premise of inclusion of higher-order processes that were neglected in earlier work.Comment: 8 pages, 3 figure

Complete measurements of anisotropic x-ray emission following recombination of highly charged ions

Synopsis We report the first systematic measurement of x-ray emission anisotropies following dielectronic, trielectronic and quadroelectronic recombination into He-like through O-like iron and krypton ions. Using the experimental data we calculated the polarization of the Kα x rays in an anisotropic plasma as a function of the plasma temperature. Unexpectedly, we found that the degree of polarization is dominated by previously neglected trielectronic and quadroelectronic recombination resonances

Measurement of the angular distribution of Dielectronic Recombination into highly charged Krypton ions

Angular distribution of x-rays emitted in the process of Dielectronic Recombination (DR) was studied at the Electron Beam Ion Trap. For this the photon emission spectra were observed along and perpendicular the electron beam propagation direction. X-ray line intensities differ drastically between the two acquired spectra. This indicates a strong alignment of the total angular momentum vector of the excited states populated by DR with respect to the electron beam propagation direction