The meV XUV-RIXS facility at UE112-PGM1 of BESSY II.

Resonant inelastic X-ray scattering in the XUV-regime has been implemented at BESSY II, pushing for a few-meV bandwidth in inelastic X-ray scattering at transition metal M-edges, rare earth N-edges and the K-edges of light elements up to carbon with full polarization control. The new dedicated low-energy beamline UE112-PGM1 has been designed to provide 1 µm vertical and 20 µm horizontal beam dimensions that serve together with sub-micrometre solid-state sample positioning as the source point for a high-resolution plane grating spectrometer and a high-transmission Rowland spectrometer for rapid overview spectra. The design and commissioning results of the beamline and high-resolution spectrometer are presented. Helium autoionization spectra demonstrate a resolving power of the beamline better than 10 000 at 64 eV with a 300 lines mm-1 grating while the measured resolving power of the spectrometer in the relevant energy range is 3000 to 6000.

Optimized highly efficient multilayer-coated blazed gratings for the tender X-ray region.

The optimized design of multilayer-coated blazed gratings (MLBG) for high-flux tender X-ray monochromators was systematically studied by numerical simulations. The resulting correlation between the multilayer d-spacing and grating blaze angle significantly deviated from the one predicted by conventional equations. Three high line density gratings with different blaze angles were fabricated and coated by the same Cr/C multilayer. The MLBG with an optimal blaze angle of 1.0° showed a record efficiency reaching 60% at 3.1 keV and 4.1 keV. The measured efficiencies of all three gratings were consistent with calculated results proving the validity of the numerical simulation and indicating a more rigorous way to design the optimal MLBG structure.

Spectromicroscopy of Nanoscale Materials in the Tender X-Ray Regime Enabled by a High Efficient Multilayer-Based Grating Monochromator.

The combination of near edge X-ray absorption spectroscopy with nanoscale X-ray imaging is a powerful analytical tool for many applications in energy technologies, catalysis, which are critical to combat climate change, as well as microelectronics and life science. Materials from these scientific areas often contain key elements, such as Si, P, S, Y, Zr, Nb, and Mo as well as lanthanides, whose X-ray absorption edges lie in the so-called tender photon energy range 1.5-5.0 keV. Neither conventional grazing incidence grating nor crystal monochromators have high transmission in this energy range, thereby yielding the tender photon energy gap. To close this gap, a monochromator setup based on a multilayer coated blazed plane grating and plane mirror is devised. The measurements show that this novel concept improves the photon flux in the tender X-ray regime by two-orders-of-magnitude enabling previously unattainable laboratory and synchrotron-based studies. This setup is applied to perform nanoscale spectromicroscopy studies. The high photon flux provides sufficient sensitivity to obtain the electronic structure of Mo in platinum-free MoNi4 nanoparticles for electrochemical energy conversion. Additionally, it is shown that the chemical bonding of nano-structures in integrated circuits can be distinguished by the electronic configuration at the Si-K edge.