Katja Frenzel

In this work, we present an end-station with two perpendicular high-efficiency soft x-ray spectrometers at the plane grating monochromator beamline in the Physikalisch-Technische Bundesanstalt laboratory at the electron storage ring BESSY II. It is designed for polarization-dependent x-ray emission spectroscopy and resonant inelastic x-ray scattering spectroscopy and covers the photon energy range from 80 to 1100 eV. Depending on the energy range to be monitored, either one of two spherical mirrors and either one of three variable line spacing gratings in each spectrometer is selected to provide optimal performance in terms of resolving power and detection yield. A calibration of the optical components and detection devices enables quantitative measurements and the possibility of the determination of x-ray fluorescence fundamental parameters in the soft x-ray range.

An operando, chemistry-resolved approach is presented for the quantitative analysis of sodium transport and speciation in hard carbon anodes during electrochemical cycling. By combining Na K-edge X-ray absorption spectroscopy with reference-free X-ray fluorescence analysis, absolute, SI-traceable sodium inventories and species-resolved sodium concentrations are determined directly under operando conditions without calibration standards. Reference spectra of relevant sodium compounds were acquired and used for spectral deconvolution, enabling quantitative determination of Na-containing interphase and conversion products. Focusing on the first galvanostatic cycle, the methodology resolves distinct sodiation and desodiation regimes characterized by different sodium uptake and release rates. The operando measurements reveal the evolution of individual sodium species and distinguish reversible sodium storage from irreversible sodium immobilization within the electrode. By directly linking electrochemical performance to localized sodium inventories and chemical speciation, the approach establishes a quantitative operando framework for mechanistic studies, material optimization, and future sodium-ion battery development.

High‐Ni layered oxides are among the most promising cathode materials for lithium‐ion batteries (LIBs) due to their high capacity. However, the reliance on Co, a scarce, expensive, and geographically constrained element, poses challenges to sustainability and large‐scale deployment. In this study, Ti is investigated as a cost‐effective and earth‐abundant substitute for Co in LiNi _1‐x Ti _x O ₂ (LNTO, x = 0.07 and 0.14), synthesized via a scalable co‐precipitation method. EXAFS analyses indicate that no obvious Jahn–Teller distortion is observed in LNTO‐1, while DFT calculations suggest that Ti substitution modulates the Ni─O electronic interaction and helps reduce the driving force for cooperative Jahn–Teller distortion within the interconnected NiO ₆ framework. In addition, it suppresses the detrimental H2–H3 phase transition and reduces internal mechanical stress during cycling. EXAFS and NEXAFS analyses further reveal that TiO ₆ octahedra act as compensatory structural units that accommodate lattice strain in both bulk and surface regions, thereby stabilizing the rhombohedral framework. As a result, the optimized LNTO‐1 ( x = 0.07) delivers a high initial discharge capacity of 197.5 mAh g ^{− 1} at 0.05 C and retains 80% capacity after 431 cycles at 0.5 C. This work provides strategic insights for the design of sustainable, high‐performance cobalt‐free Ni‐rich cathodes for next‐generation LIBs.

An improvement in the reliability and comparability of tissue characterization results is crucial for enabling further progress in cancer detection and the assessment of therapeutic effects. This can only be achieved by integrating quantitative methods into well-established qualitative characterization routines. This case study presents a hybrid metrological approach for tissue characterisation including vibrational Fourier Transform InfraRed (FTIR) spectroscopy and traceable reference-free X-Ray Fluorescence analysis (XRF). Through the combination of spatially resolved qualitative molecular information with quantitative elemental concentrations an all-encompassing sample characterisation can be provided. The study was performed on tissue sections of syngeneic murine pancreatic ductal adenocarcinoma KPC (Kras^G12D/+; Trp53^R172H/+; Pdx-1-Cre) tumours ex-vivo. Sections from healthy pancreatic tissues, sham-exposed tumours and tumours subjected to low dose radiotherapy treatment (2 Gray and 6 Gray) were analysed using both methods. Additional sample integrity studies using Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy at the carbon and nitrogen K-edges were performed to assess the effect of sample aging and XRF investigations on the samples. Results showed an increase in the concentrations of elemental biomarkers, including S, K and amide I structures in malignant pancreatic tissue compared to healthy pancreatic tissue. The exposure of tumours to 6 Gy radiation decreases the levels of these elements towards a phenotype seen in the healthy pancreas. A protocol for hybrid investigations is presented, with emphasis on the sample preparation, minimizing the impact of consecutive applied methods on their measurands, and ensuring the compatibility and reliability of achieved results. The study demonstrates the cancer recognition capabilities, and the sensitivity for low dosage radiotherapy treatment monitoring for each method individually and assesses the potential of combining molecular fingerprinting with non-destructive quantitative elemental information for tissue sample characterization.

The L-shell fluorescence yields and the Coster–Kronig factors of ruthenium (and the corresponding uncertainty) were determined for the first time experimentally by applying radiometrically calibrated instrumentation of the Physikalisch-Technische Bundesanstalt. The resulting fluorescence yields (ω L₃ = 0.0459(20), ω L₂ = 0.0415(26), ω L₁ = 0.0109(9)) and the Coster–Kronig factors (f₂₃ = 0.177(32), f₁₃ = 0.528(90), f₁₂ = 0.173(73)) agree reasonable well with parts of the data from the literature.

Using radiometrically calibrated instrumentation of the Physikalisch-Technische Bundesanstalt, the L-shell fluorescence yields and Coster–Kronig factors of tantalum (including the uncertainty budget) were experimentally determined based on transmission and X-ray fluorescence experiments. The determined fluorescence yields (ω L₃ = 0.247(12), ω L₂ = 0.278(15), ω L₁ = 0.157(12)) were independently validated through XRR-GIXRF experiments. Both the Coster–Kronig factors (f₂₃ = 0.123(84), f₁₃ = 0.328(152), f₁₂ = 0.14(11)) as well as the fluorescence yields are in good agreement with the most established databases in the field of X-ray fluorescence.