We have investigated multiphoton multiple ionization dynamics of xenon atoms using a new x-ray free-electron laser facility, SPring-8 Angstrom Compact free electron LAser (SACLA) in Japan, and ...identified that Xe(n+) with n up to 26 is produced at a photon energy of 5.5 keV. The observed high charge states (n≥24) are produced via five-photon absorption, evidencing the occurrence of multiphoton absorption involving deep inner shells. A newly developed theoretical model, which shows good agreement with the experiment, elucidates the complex pathways of sequential electronic decay cascades accessible in heavy atoms. The present study of heavy-atom ionization dynamics in high-intensity hard-x-ray pulses makes a step forward towards molecular structure determination with x-ray free-electron lasers.
Abstract
BL-774
is a control, data acquisition, and online analysis platform for addressing the requirements in future beamline experiments at SPring-8-II. To date, we have achieved implementations ...related to “robustness and flexibility” and “configuration management”. These implementations were made possible by the two-phase development workflow. The two-phase development is characterized by a dedicated rapid application development environment that beamline scientists can use rapidly and easily in real beamline environments, and web-based graphical user interfaces that
BL-774
software developers have incorporated the achievements of the beamline scientists as part of the official release of the beamline control software.
BL-774
has been introduced in two beamlines to date, and we plan to implement it in more beamlines while adding more features. We plan to integrate
BL-774
seamlessly with other systems that are currently under development in the facility, such as two-dimensional detector systems and SPring-8 data centers. By introducing
BL-774
in conjunction with other infrastructure in the facility, more advanced experimental operations, such as feedback operations based on online data analysis or remote operations from outside the beamlines, are to be expected. This paper presents the design and implementation of
BL-774
and its introduction into a beamline at SPring-8.
Synopsis We performed a wide-angle X-ray scattering experiment of single Xe nanoparticles using an X-ray free electron laser. We developed a novel analysis method that focuses on the angular ...correlation between plural Bragg spots in single-shot diffraction patterns. The angular correlations of the Bragg spots encode rich structural information and offer an evidence of twinning and stacking faults in Xe nanoparticles.
The local electronic structures of crystalline and amorphous films of zinc phthalocyanine (ZnPc) and metal-free phthalocyanine (H(2)Pc) have been studied by soft x-ray emission spectroscopy (XES). We ...found a clear crystalline structure dependence of the elastic-peak shape in the resonant XES spectra. The elastic peaks of both ZnPc and H(2)Pc are found to show an asymmetric shape due to resonant inelastic x-ray scattering (RIXS) at the nitrogen sites for the α-crystalline films, but not for the amorphous films. The observed RIXS feature is ascribed to the charge transfer excitation due to the Raman-active intermolecular interaction, which dominates the excited-electron dynamics in α-crystalline phthalocyanine films.
This article presents a method for precisely measuring the charge spread inside a silicon sensor, before it is sampled by the pixels of an X-ray imaging detector. The shape of the charge spread or ...pre-sampled point spread function (PSF) of the silicon sensor was demonstrated with a sub-micrometer resolution. The measurement setup comprises quasi-monochromatic X-ray beams emitted by a synchrotron radiation source, 5-μm-diameter tungsten pinhole, sub-μm-resolution X-ray beam profiler, and photodiode array in automation mode for step-scanning measurements. We obtained a value of 16.5–17.1 μm (full width at half-maxima; sensor thickness: 650 μm; bias voltage: 750 V) based on preliminary experiments using 7.3 keV X-rays at BL19LXU of SPring-8. This value is consistent with the expected value obtained from the convolution of the beam profiles and pre-sampled PSFs corresponding to multiple photons for a dopant density of ∼1012cm−3 within a range of approximately 1 μm. We believe that our measurement method has sufficient potential for evaluating the pre-sampled PSF of a photodiode array with an accuracy of 1 μm or less. The single-photon capability of imaging detectors depends on the detector noise as well as the pre-sampled PSF. Our measurement method, with high spatial resolution, is beneficial in the sense that it optimizes the pixel design of X-ray image sensors using a sample piece with a limited number of pixels.
Bacteriorhodopsin (bR) is a light-driven proton pump and a model membrane transport protein. We used time-resolved serial femtosecond crystallography at an x-ray free electron laser to visualize ...conformational changes in bR from nanoseconds to milliseconds following photoactivation. An initially twisted retinal chromophore displaces a conserved tryptophan residue of transmembrane helix F on the cytoplasmic side of the protein while dislodging a key water molecule on the extracellular side. The resulting cascade of structural changes throughout the protein shows how motions are choreographed as bR transports protons uphill against a transmembrane concentration gradient.
We have studied charge migration and dissociation in iodine-substituted methane molecules using extremely intense and short 5.5 keV free electron laser pulses from the SACLA XFEL facility. Multiple ...core ionization down to I 2p subshells creates highly charged molecular states, the fragmentation of which was studied by ion momentum imaging multiparticle coincidence technique. We report experimental and modeling results on various dissociation pathways, fragment momentum correlations, and kinetic energy releases.
The electronic structure of bases in DNA duplexes was investigated by resonant photoemission spectroscopy near the Fermi level, in order to specify charge migration mechanisms. We observed a kinetic ...energy shift of N-KLL Auger electrons and an intensity enhancement of valence electrons on the resonant photoemission spectra for both poly(dG).poly(dC) and poly(dA).poly(dT) DNAs. These directly show the localized unoccupied states of the bases. We conclude that the charge hopping model is pertinent for electric conduction in a DNA duplex, when electrons pass through the unoccupied states.
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