A5091898373- Advanced X-ray Imaging Techniques
- Spectroscopy and Quantum Chemical Studies
- Laser-Matter Interactions and Applications
- Advanced Electron Microscopy Techniques and Applications
- X-ray Spectroscopy and Fluorescence Analysis
- Perovskite Materials and Applications
- Crystallography and Radiation Phenomena
- Particle Accelerators and Free-Electron Lasers
- Advanced Chemical Physics Studies
- Quantum, superfluid, helium dynamics
- Atomic and Subatomic Physics Research
- Solid-state spectroscopy and crystallography
- Quantum Dots Synthesis And Properties
- Photochemistry and Electron Transfer Studies
- Photosynthetic Processes and Mechanisms
- Electron Spin Resonance Studies
- Porphyrin and Phthalocyanine Chemistry
- Hemoglobin structure and function
- Nuclear Physics and Applications
- Mass Spectrometry Techniques and Applications
- Terahertz technology and applications
- Atomic and Molecular Physics
- Random lasers and scattering media
- Advanced NMR Techniques and Applications
- Photoreceptor and optogenetics research
Argonne National Laboratory
2017-2025
Paul Scherrer Institute
2019-2024
École Polytechnique Fédérale de Lausanne
2014-2021
Institut Supérieur de l'Information et de la Communication
2016
Centre d'Imagerie BioMedicale
2016
The “hole” story of water ionization direct observation the cationic hole H 2 O + that is formed in liquid after has been a long-standing experimental challenge. Previous attempts using optical and ultraviolet techniques have failed to reveal its key spectroscopic signature during ultrafast transformation into OH radical. Loh et al. address this gap by intense, x-ray pulses from an free electron laser at ∼530 volts. They found compelling evidence for formation decay radical proton transfer...
In quantum systems, coherent superpositions of electronic states evolve on ultrafast timescales (few femtosecond to attosecond, 1 as = 0.001 fs 10^{-18} s), leading a time dependent charge density. Here we exploit the first attosecond soft x-ray pulses produced by an free-electron laser induce core-hole excitation in nitric oxide. Using additional circularly polarized infrared pulse create clock time-resolve electron dynamics, and demonstrate control motion tuning photon energy pulse....
Abstract Diffraction-before-destruction imaging with ultrashort X-ray pulses can visualize non-equilibrium processes, such as chemical reactions, sub-femtosecond precision in the native environment. Here, a nanospecimen diffracts single flash before it disintegrates. The sample structure be reconstructed from coherent diffraction image (CDI). State-of-the-art snapshots lack high spatial resolution because of weak signal. Bleaching effects photo-ionization significantly restrain brightness...
We report on an element-selective study of the fate charge carriers in photoexcited inorganic CsPbBr3 and CsPb(ClBr)3 perovskite nanocrystals toluene solutions using time-resolved X-ray absorption spectroscopy with 80 ps time resolution. Probing Br K-edge, Pb L3-edge, Cs L2-edge, we find that holes valence band are localized at atoms, forming small polarons, while electrons appear as delocalized conduction band. No signature either electronic or structural changes is observed L2-edge. The...
Free-electron lasers provide a source of x-ray pulses short enough and intense to drive nonlinearities in molecular systems. Impulsive interactions driven by these way create probe valence electron motions with high temporal spatial resolution. Observing electronic is crucial understand the role coherence chemical processes. A simple nonlinear technique for probing motion, impulsive stimulated Raman scattering (ISXRS), involves single interaction produce coherent superposition states. We...
Resonant inelastic x-ray scattering (RIXS) provides remarkable opportunities to interrogate ultrafast dynamics in liquids. Here we use RIXS study the fundamentally and practically important hydroxyl radical liquid water, OH(aq). Impulsive ionization of pure water produced a short-lived population OH(aq), which was probed using femtosecond x-rays from an free-electron laser. We find that reveals localized electronic transitions are masked ultraviolet absorption spectrum by strong...
The development of next-generation perovskite-based optoelectronic devices relies critically on the understanding interaction between charge carriers and polar lattice in out-of-equilibrium conditions. While it has become increasingly evident for CsPbBr3 perovskites that Pb–Br framework flexibility plays a key role their light-activated functionality, corresponding local structural rearrangement not yet been unambiguously identified. In this work, we demonstrate photoinduced changes system...
X-ray free-electron lasers (FELs) are state-of-the-art scientific tools capable to study matter on the scale of atomic processes. Since initial operation FELs more than a decade ago, several facilities with upgraded performance have been put in operation. Here we present first lasing results Athos, soft FEL beamline SwissFEL at Paul Scherrer Institute Switzerland. Athos features an undulator layout based short APPLE-X modules providing full polarisation control, interleaved small magnetic...
Abstract Intense x-ray free-electron laser (XFEL) pulses hold great promise for imaging function in nanoscale and biological systems with atomic resolution. So far, however, the spatial resolution obtained from single shot experiments lags averaging static experiments. Here we report on a combined computational experimental study about ultrafast diffractive of sucrose clusters which are benchmark organic samples. Our theoretical model matches data water window to keV regime. The large-scale...
A new experimental technique uses an x-ray free-electron laser to reveal charge dynamics within a molecule following removal of electron, paving the way for broader understanding molecular transfer.
Significance We demonstrate the occurrence of tryptophan (Trp) to heme electron transfer (ET) in ferrous myoglobins by ultrafast UV spectroscopy. The ET gives rise theoretically predicted, low-valence Fe(II)(porph ●− ) anion radical, which we observe for first time our knowledge under physiological conditions. These results highlight generality Trp–porphyrin events proteins and question systematic use Trp fluorescence FRET studies protein dynamics.
Ligand substitution reactions are common in solvated transition metal complexes, and harnessing them through initiation with light promises interesting practical applications, driving interest new means of probing their mechanisms. Using a combination time-resolved x-ray absorption spectroscopy hybrid quantum mechanics/molecular mechanics (QM/MM) molecular dynamics simulations near-edge calculations, we elucidate the mechanism photoaquation model system iron(ii) hexacyanide, where UV...
We present an approach to determine the absolute thickness profile of flat liquid jets, which takes advantage information thin film interference combined with light absorption, both captured in a single microscopic image. The feasibility proposed method is demonstrated on our compact experimental setup used generate micrometer thin, free-flowing jet sheets upon collision two identical laminar cylindrical jets. Stable operation was achieved over several hours vacuum (10−4 mbar), making system...
The concomitant motion of electrons and nuclei on the femtosecond time scale marks fate chemical biological processes. Here we demonstrate ability to initiate track ultrafast electron rearrangement bond breaking site-specifically in real for carbon monoxide diatomic molecule. We employ a local resonant x-ray pump at oxygen atom probe shifts core-electron binding energy. observe charge redistribution accompanying core-excitation followed by Auger decay, eventually leading dissociation hole...
We demonstrate the generation of widely tunable two-color x-ray free-electron laser (FEL) pulses at SwissFEL. In a split-undulator configuration, each color is produced in different undulator section, and chicane between two sections allows for variable time separation up to 500 fs. show an unprecedented photon energy ratio colors about three (350 915 eV), with individual pulse having peak power few gigawatts duration down femtosecond level. Moreover, we reduction required length via optical...
The recent demonstration of isolated attosecond pulses from an X-ray free-electron laser (XFEL) opens the possibility for probing ultrafast electron dynamics at wavelengths. An established experimental method is transient absorption spectroscopy, where spectrum measured by scanning central photon energy and recording resultant photoproducts. spectral bandwidth inherent to wide compared resonant features typically probed, which generally precludes application this technique in regime. In...
The differentially pumped rare-gas filter at the end of VUV beamline Swiss Light Source has been adapted to house a windowless absorption cell for gases. Absorption spectra can be recorded from 7 eV up 21 photon energies routinely, as shown by new water and nitrous oxide spectrum. By large, agree with previously published ones both in terms resonance cross sections, but that N 2 O exhibits small shift {\tilde{\bf D}} band tentative fine structures have not yet fully described. This setup...
Previous single-pulse extreme ultraviolet and x-ray coherent diffraction studies revealed that superfluid $^{4}\mathrm{He}$ droplets obtained in a free jet expansion acquire sizable angular momentum, resulting significant centrifugal distortion. Similar experiments with normal fluid $^{3}\mathrm{He}$ may help elucidate the origin of large degree rotational excitation highlight similarities differences dynamics droplets. Here, we present comparison shapes isolated following corresponding...
We present a compact passively phase-stabilized ultra-broadband 2D Fourier transform setup. A gas (argon)-filled hollow core fiber pumped by an amplified Ti:Al2O3 laser is used as light source providing spectral range spanning from 420 to 900 nm. Sub-10-fs pulses were obtained using deformable mirror-based pulse shaper. probe the nonlinear response of Rhodamine 101 90 nm bandwidth and resolve vibrational coherences 150 fs period in ground state.
Two-dimensional Fourier transform spectroscopy is a promising technique to study ultrafast molecular dynamics. Similar transient absorption spectroscopy, more complete picture of the dynamics requires broadband laser pulses observe changes over large enough bandwidth, exceeding inhomogeneous width electronic transitions, as well separation between or vibronic transitions interest. Here, we present visible 2D spectra series dye molecules and report vibrational coherences with frequencies up...
Abstract The charge-integrating hybrid silicon pixel detector JUNGFRAU has found widespread use at free-electron laser and synchrotron facilities. was designed for with hard X-rays; yet, because of its low noise, high dynamic range, position resolution, scalable size, is interest soft X-ray applications. We discuss improvements the readout chip alterations entrance window back sensor that facilitate low-energy detection. first case improved system a beamline demonstrates single photon...
Clusters in 3 He and 4 nanodroplets reveal markedly different shapes showcasing the effect of superfluidity on aggregation.
Abstract X-ray photoelectron spectroscopy (XPS) measures the binding energy of core-level electrons, which are well-localised to specific atomic sites in a molecular system, providing valuable information on local chemical environment. The technique relies measuring spectrum upon x-ray photoionisation, and resolution is often limited by bandwidth ionising pulse. This particularly problematic for time-resolved XPS, where desired time enforces fundamental lower limit source. In this work, we...