arXiv subjects

Clemens Weninger

Publications and source records attributed to Clemens Weninger.

6 recordsLinked to original sources

arXiv2026

Data acquisition from high-rate detectors at MAX IV

At MAX IV pixelated area detectors are operated at high frame rates to take advantage of the X-ray beam properties available from the fourth generation synchrotron in scattering, diffraction and imaging applications. A variety of photon counting and charge integrating detectors and sCMOS cameras have been integrated into a common data acquisition (DAQ) system in which data are streamed to a central Kubernetes cluster, mounting an IBM Storage Scale (GPFS) file system. The DAQ system provides live feedback from the detectors/cameras and extends to enable on-the-fly data processing. Control system integration via Tango provides a standardised single interface for controlling all DAQ components. Starting from an overview of the detector types in use, we describe the design and implementation of the MAX~IV detector-DAQ system and report a quantitative study of its performance in terms of data throughput and detector operating rates.

physics.ins-det↗

arXiv2025

Observation of Multiplet Lines in Seeded Stimulated Mn Kα1 X-ray Emission

We report the successful resolution of the multiplet structure of the Kα1 x-ray emission in manganese (Mn) complexes through seeded stimulated X-ray emission spectroscopy (seeded S-XES). By employing a femtosecond pump pulse above the Mn K edge to generate simultaneous 1s core-holes, and a second-color tunable seed pulse to initiate the stimulated emission process, we were able to enhance individual lines within the Kα1 emission. This approach allows to resolve the fine multiplet features that are obscured by the life-time broadening in conventional Mn Kα XES. The work builds on our previous observation that S-XES from Mn(II) and Mn(VII) complexes pumped at high intensities can exhibit stimulated emission without sacrificing the chemical sensitivity to oxidation states. This technique opens the door to controlled high-resolution electronic structure spectroscopy in transition metal complexes beyond core hole life time broadening with potential applications in catalysis, inorganic chemistry, and materials science.

physics.chem-ph↗

arXiv2025

Attosecond Inner-Shell Lasing at Angstrom Wavelengths

Since the invention of the laser nonlinear effects such as filamentation, Rabi-cycling and collective emission have been explored in the optical regime leading to a wide range of scientific and industrial applications. X-ray free electron lasers (XFELs) have led to the extension of many optical techniques to X-rays for their advantages of angstrom scale spatial resolution and elemental specificity. One such example is XFEL driven population inversion of 1s core hole states resulting in inner-shell K$α$ (2p to 1s) X-ray lasing in elements ranging from neon to copper, which has been utilized for nonlinear spectroscopy and development of next generation X-ray laser sources. Here we show that strong lasing effects, similar to those observed in the optical regime, can occur at 1.5 to 2.1 angstrom wavelengths during high intensity (> ${10^{19}}$ W/cm${^{2}}$) XFEL driven inner-shell lasing and superfluorescence of copper and manganese. Depending on the temporal substructure of the XFEL pump pulses(containing ${~10^{6}}$ - ${10^{8}}$ photons) i, the resulting inner-shell X-ray laser pulses can exhibit strong spatial inhomogeneities as well as spectral splitting, inhomogeneities and broadening. Through 3D Maxwell Bloch theory we show that the observed spatial inhomogeneities result from X-ray filamentation, and that the spectral splitting and broadening is driven by Rabi cycling with sub-femtosecond periods. Our simulations indicate that these X-ray pulses can have pulse lengths of less than 100 attoseconds and coherence properties that open the door for quantum X-ray optics applications.

physics.optics↗

arXiv2021

Generation of Intense Phase-Stable Femtosecond Hard X-ray Pulse Pairs

Coherent nonlinear spectroscopies and imaging in the X-ray domain provide direct insight into the coupled motions of electrons and nuclei with resolution on the electronic length and time scale. The experimental realization of such techniques will strongly benefit from access to intense, coherent pairs of femtosecond X-ray pulses. We have observed phase-stable X-ray pulse pairs containing more thank 3 x 10e7 photons at 5.9 keV (2.1 Angstrom) with about 1 fs duration and 2-5 fs separation. The highly directional pulse pairs are manifested by interference fringes in the superfluorescent and seeded stimulated manganese K-alpha emission induced by an X-ray free-electron laser. The fringes constitute the time-frequency X-ray analogue of the Young double-slit interference allowing for frequency-domain X-ray measurements with attosecond time resolution.

physics.atom-ph↗

arXiv2021

Nanoscale heterogeneous dynamics probed by nanosecond x-ray speckle visibility spectroscopy

We report observations of nanosecond nanometer scale heterogeneous dynamics in a free flowing colloidal jet revealed by ultrafast x-ray speckle visibility spectroscopy. The nanosecond double-bunch mode of the Linac Coherent Light Source free electron laser enabled the production of pairs of femtosecond coherent hard x-ray pulses. By exploring the anisotropic summed speckle visibility which relates to the correlation functions, we are able to evaluate not only the average particle flow rate in a colloidal nanoparticle jet, but also the heterogeneous flow field within. The reported methodology presented here establishes the foundation for the study of nano- and atomic-scale heterogeneous fluctuations in complex matter using x-ray free electron laser sources.

cond-mat.soft↗

arXiv2018

Carrier-Specific Femtosecond XUV Transient Absorption of PbI2 Reveals Ultrafast Nonradiative Recombination

Femtosecond carrier recombination in PbI2 is measured using tabletop high-harmonic extreme ultraviolet (XUV) transient absorption spectroscopy and ultrafast electron diffraction. XUV absorption from 45 eV to 62 eV measures transitions from the iodine 4d core level to the conduction band density of states. Photoexcitation at 400 nm creates separate and distinct transient absorption signals for holes and electrons, separated in energy by the 2.4 eV band gap of the semiconductor. The shape of the conduction band and therefore the XUV absorption spectrum is temperature dependent, and nonradiative recombination converts the initial electronic excitation to thermal excitation within picoseconds. Ultrafast electron diffraction (UED) is used to measure the lattice temperature and confirm the recombination mechanism. The XUV and UED results support a 2nd-order recombination model with a rate constant of 2.5x10-9 cm3/s.

cond-mat.mtrl-sci↗