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A readout system based on the Timepix4 ASIC, is being developed for photon science. The TEMPUS detector can be operated in two distinct modes: a photon counting mode, which allows for conventional full-frame readout at rates up to 40 kfps; and an event-driven time-stamping mode, which allows excellent time resolution in the nanosecond regime in measurements with moderate X-ray flux. In this paper, we introduce the initial prototype, a single-chip system, and present the first results obtained at PETRA III and ESRF., Comment: 19 pages, 6 figures

Coherent control of quantum dynamics is key to a multitude of fundamental studies and applications alike. In the visible or longer-wavelength domains, near-resonant light fields have become the primary tool to control electron dynamics. Recently, coherent control in the extreme-ultraviolet range was demonstrated, with timing stability of the applied light fields in the few-attosecond range. At hard x-ray energies, M\"ossbauer nuclei feature narrow nuclear resonances, and spectroscopy of these resonances is a widespread tool to study magnetic, structural and dynamical properties of matter. It has been shown that the power and scope of M\"ossbauer spectroscopy can be significantly advanced using various control techniques. However, the coherent control of atomic nuclei using near-resonant x-ray fields remains an open challenge, also because of the extreme stability requirements on the x-ray light in the few-zeptosecond range. Here, we demonstrate such control, and use the relative phase of two x-ray pulses to switch the nuclear dynamics between stimulated emission and enhanced coherent excitation. For this, we suggest and implement a method to shape single pulses delivered by modern x-ray facilities into tunable double-pulses, with the desired stability on the few-zeptosecond level. Our results unlock coherent optical control for nuclei, and pave the way for nuclear Ramsey spectroscopy and spin-echo-like techniques, which not only provide key concepts for advancing nuclear quantum optics, but also essential ingredients for possible x-ray clocks and frequency standards. As a long-term perspective, we envision time-resolved studies of nuclear out-of-equilibrium dynamics, which is a long-standing open challenge in M\"ossbauer science., Comment: 12 pages, 11 figures

We have tested the new experimental techniques in the M\"ossbauer spectroscopy with Synchrotron M\"ossbauer Source by using the polarization analysis of the reflected radiation. In particular we have shown that the dichroic components in M\"ossbauer spectra create the scattering intensity with "rotated" polarization. The angular dependence for such component in the reflected signal is characterized by the peak near the critical angle of the total external reflection, and in the case of the collinear antiferromagnetic interlayer ordering the "magnetic" maxima on the reflectivity curve are formed mainly by this "rotated" polarization. The first experiment on M\"ossbauer reflectivity with selection of the "rotated" polarization shows the expected peak near the critical angle. The measured M\"ossbauer reflectivity spectra of the "rotated" polarization near the critical angle are rather different from the M\"ossbauer reflectivity spectra, measured without polarization analysis. They contain a smaller number of lines and can simplify the interpretation of the poorly resolved spectra. The enhanced surface sensitivity of the new technique is discussed., Comment: 17 pages, 8 figures

We present a synchrotron-based X-ray scattering technique which allows disentangling magnetic properties of heterogeneous systems with nanopatterned surfaces. This technique combines the nmrange spatial resolution of surface morphology features provided by Grazing Incidence Small Angle X-ray Scattering and the high sensitivity of Nuclear Resonant Scattering to magnetic order. A single experiment thus allows attributing magnetic properties to structural features of the sample; chemical and structural properties may be correlated analogously. We demonstrate how this technique shows the correlation between structural growth and evolution of magnetic properties for the case of a remarkable magnetization reversal in a structurally and magnetically nanopatterned sample system.

Nuclear inelastic scattering in conjunction with density functional theory (DFT) calculations has been applied for the identification of vibrational modes of the high-spin ferric and the high-spin ferrous iron-sulfur center of a rubredoxin-type protein from the thermophylic bacterium Pyrococcus abysii.

Nuclear inelastic scattering of synchrotron radiation has been used now since 10 years as a tool for vibrational spectroscopy. This method has turned out especially useful in case of large molecules that contain a M\"ossbauer active metal center. Recent applications to iron-sulfur proteins, to iron(II) spin crossover complexes and to tin-DNA complexes are discussed. Special emphasis is given to the combination of nuclear inelastic scattering and density functional calculations.