Recent progress in ultrafast x-ray sources helped establish x-rays as an important tool for probing lattice and magnetic dynamics initiated by femtosecond optical pulses. Here, we explore the potential of ultrashort hard x-ray pulses for driving magnetic dynamics. We use a transient grating technique in which a spatially periodic x-ray excitation pattern gives rise to material excitations at a well-defined wave vector, whose dynamics are monitored via diffraction of an optical probe pulse. The excitation of a ferrimagnetic gadolinium bismuth iron garnet film placed in an external tilted magnetic field by x-rays at the Gd L3 edge results in both magnetic and non-magnetic transient gratings whose contributions to the diffracted signal are separated by polarization analysis. We observe the magnetization precession at both longitudinal acoustic and spin wave frequencies. An analysis with the Landau-Lifshitz-Gilbert equation indicates that the magnetization precession is driven by strain resulting from thermal expansion induced by absorbed x-rays. The results establish x-ray transient gratings as a tool for driving coherent phonons and magnons, with the potential of accessing wave vectors across the entire Brillouin zone.

Abstract Electrochemical CO2 reduction (eCO2R) is a sustainable strategy for converting CO2 into value-added chemicals. Here, we report the Cu-azolate metal−organic framework (MOF) CuBBTA (Cu2Cl2-bbta, MAF-X29) as a stable electrocatalyst for eCO2R in a zero-gap electrolyzer. CuBBTA was spray-coated onto carbon paper using either PTFE or Nafion binders to form gas diffusion electrodes that achieved Faradaic efficiencies of up to 50% for carbon-containing products (CH4, C2H4, and CO) at current densities as high as 100 mA cm−2 under a flow of CO2. Post-electrolysis studies confirmed retention of the MOF structure. DFT calculations reveal that CO2 reduction proceeds via COOH* and CO* intermediates, with a thermodynamically favourable and kinetically accessible CO*−CO* dimerization pathway for ethylene formation. Importantly, polymer binder selection significantly influences product selectivity. While PTFE favours methane formation, Nafion shifts selectivity toward CO, highlighting the critical yet underexplored role of electrode environment in MOF-based eCO2R catalysis.

The development of X-ray Free Electron Lasers (XFELs) unlocked new possibilities in many areas of science. These facilities routinely produce femtosecond X-ray pulses with extremely high peak brilliance, enabling time-resolved X-ray spectroscopy experiments to study ultrashort phenomena in matter. However, many fundamental electron processes in atoms, molecules, and clusters are still unreachable by the XFEL-based time-resolved methods. Recently, an innovative methodology called X-ray Chronoscopy was introduced to address some current time resolution limits typically encountered at XFEL. Herein, we assess the ability of X-ray Chronoscopy to track electron dynamics in an optical pump/X-ray probe XFEL experiment. By employing numerical simulations, we showed that the proposed method could determine femtosecond relaxation rates in matter while mitigating the main issues related to optical pump/X-ray probe experiments at XFELs, such as pump-probe arrival time jitter. We anticipate that with the ongoing advent of temporal diagnostic tools, the implementation of X-ray Chronoscopy at XFEL would complement the information obtained from X-ray spectroscopy, providing a complete picture of the sample's electronic structure.

Precise control and characterization of nanomaterials at working conditions are essential for further rational applications in many areas important for modern society. Penetrating properties of X-ray radiation in combination with advanced spectroscopy schemes are an ideal tool to investigate modifications of nanomaterials with extraordinary precision. Here, we present preliminary results on the controlled oxidation of copper nanoparticles and exploration of X-ray absorption spectroscopy to follow electronic and structural changes. The described pilot experiment raises questions on the applicability of high energy resolution X-ray detection schemes in potential future investigations aimed at following reversible reduction/oxidation processes at nanoparticle surfaces.

To fully exploit ultra-short X-ray pulse durations routinely available at X-ray free-electron lasers to follow out-of-equilibrium dynamics, inherent arrival time fluctuations of the X-ray pulse with an external perturbing laser pulse need to be measured. In this work, two methods of arrival time measurement were compared to measure the arrival time jitter of hard X-ray pulses. The methods were photoelectron streaking by a THz field and a transient refractive index change of a semiconductor. The methods were validated by shot-to-shot correction of a pump–probe transient reflectivity measurement. An ultimate shot-to-shot full width at half-maximum error between the devices of 19.2 ± 0.1 fs was measured.

Use of THz photoelectron streaking as an arrival time-tool is presented. Complexities in calibration of the THz field as well as high fidelity, single shot photoelectron spectra giving rise to sources of errors is discussed.

With this study, we present the development of a transportable x-ray emission spectrometer (XES) that was realized in a net time of 20 h, in order to verify the presence of Platinum (Pt) in gold Celtic coins belonging to 3rd-1st century BCE. Prior to the XES study, measurements using Scanning Electron Microscopy coupled with Energy Dispersive Spectroscopy (SEM-EDS) revealed that the coins were made of highly concentrated gold (Au) alloy with trace amounts of bismuth (Bi) and, in one case, osmium (Os) and iridium (Ir). Os and Ir together with Pt and other components belong to the Platinum Group Elements (PGE). They form inclusions in ancient gold alloys and their presence is significant in provenance studies since they indicate the use of alluvial gold. Detection of platinum trace elements in a golden matrix is not possible using energy dispersive x-ray emission techniques (SEM-EDS, ED-XRF, or PIXE) because of the limited energy resolution of the Si detectors. A way to overcome this problem is by using a high-resolution wavelength dispersive x-ray emission technique. For this purpose, we built a crystal spectrometer in Von-Hamos geometry. In the framework of this study three samples/coins have been measured, and the presence of Pt was verified in one of them. The limitations of our spectrometer are critically evaluated and ways to optimize the performance of the spectrometer are discussed.

PolyX is a compact bending magnet beamline under construction at National Synchrotron Radiation Centre SOLARIS, which will be available to users in mid-2023. The beamline is focused on X-ray microimaging and microspectroscopy in the tender/hard (4-15 keV) X-ray energy range. The name PolyX comes from polycapillary X-ray optics that will be extensively used for efficient X-ray focusing and from the possibility of using polychromatic or broadband X-rays to increase the rather low flux from the SOLARIS bending magnet in the hard X-ray energy range. Polycapillary optics will provide focal spots with sizes of 8-200 mu m. Single bounce ellipsoidal capillary is expected to provide a similar to 2 mu m focal spot size. The main experimental techniques at PolyX will be X-ray absorption and phase-contrast imaging and microtomography, micro-X-ray fluorescence imaging and micro-X-ray absorption spectroscopy. This paper presents the concept of PolyX beamline and preliminary "white" beam commissioning results.

From the commonly known metal-based chemotherapeutics, like cisplatin, there is ongoing interest in searching for some of their alternatives, including copper complexes containing organic groups. In this paper, we report the results of the preliminary examination of copper-based compounds, which are studied with the use of the laboratory XAS setup, that are compared with data obtained at the synchrotron facility. Identification of spectral features and oxidation state of copper was successfully performed based only on the laboratory data, however, some limitation of this test apparatus is also reported. Additionally, we performed first testing of the laboratory XAS spectrometer to study more complex compounds, which could be used in anticancer therapy, than metallic foils, which are usually used to estimate the experimental capabilities of such setups.

With the recent progress regarding the development of x-ray instrumentation, compact x-ray spectrometers are becoming more and more popular as they allow x-ray absorption spectroscopy (XAS) and x-ray emission spectroscopy (XES) studies at the research institutes laboratories. Such setups provide a cost-effective tool for routine sample characterization with unlimited access and are of great utility in feasibility studies preceding the experiments at synchrotrons and x-ray free-electron lasers (XFELs). Herein, we present the operation and capabilities of the von Hamos type x-ray spectrometer in x-ray absorption spectra measurement for various 3d metal elements. Results allowed us to establish the photon counting performance of the setup, demonstrating a possible range of applications of the in-house x-ray spectroscopy apparatus.

The SOLARIS synchrotron located in Krakow, Poland, is a third-generation light source operating at medium electron energy. The first synchrotron light was observed in 2015, and the consequent development of infrastructure lead to the first users’ experiments at soft X-ray energies in 2018. Presently, SOLARIS expands its operation towards hard X-rays with continuous developments of the beamlines and concurrent infrastructure. In the following, we will summarize the SOLARIS synchrotron design, and describe the beamlines and research infrastructure together with the main performance parameters, upgrade, and development plans.

X-ray spectroscopy is a demanded tool across multiple user communities. Here we report on a new station for X-ray emission spectroscopy at the Extreme Light Infrastructure Beamlines Facility. The instrument utilizes the von Hamos geometry and works with a number of different sample types, notably including liquid systems. We demonstrate a simple and reliable method for source position control using two cameras. This approach addresses energy calibration dependence on sample position, which is a characteristic source of measurement uncertainty for wavelength dispersive spectrometers in XES arrangement. We also present a straightforward procedure for energy calibration of liquid and powder samples to a thin film reference. The developed instrumentation enabled us to perform the first experimental determination of the Kα lines of liquidized K3Fe(CN)6 as well as powdered and liquidized FeNH4(SO4)2. Finally, we report on proof-of-principle use of a colliding jet liquid sample delivery system in an XES experiment.

Synchrotrons are brilliant sources of X-ray radiation used in a variety of methods to study the structure of matter and dynamics of processes on the atomic scale. X-ray spectroscopy methods at synchrotrons are typically combined with the beam monochromatization which guarantees better energy resolution but also reduces orders of magnitude the photon flux incident on the sample and thus wastes the vast majority of the photons produced. Here we report on the commissioning of an X-ray spectrometer at the PolyX beamline of SOLARIS specialized in application of white, broadband and monochromatic X-ray beam in multimodal microimaging, microtomography and microscpectroscopic studies. The spectrometer was used to acquire good quality Fe K-edge X-ray absorption spectrum over about 120 eV-range within seconds. In this work we present the first X-ray absorption spectrum measured using a synchrotron white beam in combination with a von Hámos geometry-based spectrometer.

Analysis of samples in the liquid environment using X-ray spectroscopy techniques is a very attractive approach as it provides specimen characterization in its native conditions thanks to the penetrating properties of X-rays. However, very often due to challenging synthesis procedures and the high cost of specimens it is difficult to obtain a sample in quantities for optimal measurement. Additionally, nanoparticles (NPs) aqueous suspensions are often not stable and undergo agglomeration and sedimentation processes that can be avoided either by sonication or sample stirring. Relatively small sample volumes and intrinsic agglomeration processes make X-ray spectroscopy measurements challenging especially when long periods are needed for the collection of high-quality data. To address both issues, we developed dedicated sample system that allows measurements down to few tens of μL of the liquid sample with capability of continuous stirring of the suspension. The X-ray spectroscopy measurements of ZnO nanoparticles suspension in water showed a stable signal for hours of acquisition time. On the other hand, in the absence of stirring, agglomeration and subsequent sedimentation processes were visible already within few minutes with maximum sedimentation rate of 2.5% of concentration loss in the beam field per minute.

X-ray free electron lasers (XFELs) have provided scientists opportunities to study matter with unprecedented temporal and spatial resolutions. However, access to the attosecond domain (i.e., below 1 femtosecond) remains elusive. Herein, a time-dependent experimental concept is theorized, allowing us to track ultrafast processes in matter with sub-fs resolution. The proposed X-ray chronoscopy approach exploits the state-of-the-art developments in terahertz streaking to measure the time structure of X-ray pulses with ultrahigh temporal resolution. The sub-femtosecond dynamics of the saturable X-ray absorption process is simulated. The employed rate equation model confirms that the X-ray-induced mechanisms leading to X-ray transparency can be probed via measurement of an X-ray pulse time structure.

The electronic structure of transition-metal oxides is a key component responsible for material's optical and chemical properties. Specifically for metal-oxide structures, the crystal-field interaction determines the shape, strength, and occupancy of electronic orbitals. Consequently, the crystal-field splitting and resulting unoccupied state populations can be foreseen as modeling factors of the photochemical activity. Herein, we study the formation of crystal-field effects during thermal oxidation of titanium in an ambient atmosphere and range of temperatures. The X-ray absorption spectroscopy is employed for quantitative analysis of average t2g-eg crystal-field splitting (Δoct) and relative t2g/eg bands occupancy. The obtained result shows that Δoct changes as a function of temperature from 1.97 eV for a passive oxide layer created on a Ti metal surface at room temperature to 2.41 eV at 600 °C when the material changes into the TiO2 rutile phase. On the basis of XAS data analysis, we show that the Δoct values determined from L2 and L3 absorption edges are equal, indicating that the 2p1/2 and 2p3/2 core holes screen the t2g and eg electronic states in a similar manner.

Aqueous iron (III) oxide nanoparticles were irradiated with pure self-amplified spontaneous emission (SASE) X-ray free-electron laser (XFEL) pulses tuned to the energy around the Fe K-edge ionization threshold. For each XFEL shot, the incident X-ray pulse spectrum and Fe Kβ emission spectrum were measured synchronously with dedicated spectrometers and processed through a reconstruction algorithm allowing for the determination of Fe Kβ resonant X-ray emission spectroscopy (RXES) plane with high energy resolution. The influence of the number of X-ray shots employed in the experiment on the reconstructed data quality was evaluated, enabling the determination of thresholds for good data acquisition and experimental times essential for practical usage of scarce XFEL beam times.

In the probe-before-destroy methodology, developed with the advent of X-ray free-electron lasers, the investigated system is probed with an ultra-short (femtosecond) X-ray pulse within time shorter than that the X-rayinduced damage needs to propagate.Radiation damage is typically considered in terms of the Coulomb explosion which needs about 50 fs to induce observable effects in the material structure.It has been, however, shown that the much faster electronic structure change has also a significant influence on the X-ray emission spectroscopy data and may alter the X-ray diffraction patterns.This work reports on energy and time distribution of photoelectrons induced in water by an X-ray pulse with properties typical for an X-ray free-electron laser operated in the intensity regime below the sequential photoionization regime.The electron flux was simulated on the basis of a kinetic model and was found to be significant over the course of the X-ray pulse duration.The presented findings call for consideration of the X-ray-induced electrons in studies on solutions and samples embedded in matrices.

A new modification of a table-top laser-driven water-jet plasma X-ray source has been successfully implemented and commissioned at the Extreme Light Infrastructure (ELI) Beamlines user facility. In order to preserve the broadband nature of the source for spectroscopic experiments, a polycapillary lens was initially chosen as the focusing element. Generally, polycapillary X-ray optics have a narrow photon acceptance angle and small field of view, making alignment complicated and time-consuming. This contribution demonstrates a straightforward, reliable and reproducible procedure for aligning polycapillary focusing optics with broadband X-rays. The method involves a pre-alignment step where two X-ray slits are mounted orthogonally on opposite sides of a 3D-printed cylindrical polycapillary holder. This helps to precisely determine the optical axis of the X-ray beam. Subsequent mounting of the polycapillary in the pre-aligned holder with the slits removed allowed for immediate transmission of the X-ray photons through the optics and has provided a good starting point for fine alignment.