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.
We developed micro-focusing Kirkpatrick-Baez (K-B) mirror optics for the X-ray free electron laser (XFEL) at the SPring-8 Angstrom Compact free electron Laser (SACLA) facility in Japan. The K-B ...focusing mirrors have a spatial acceptance of 600 × 600 μm2 and ultra-precision surfaces. A manipulator for precise alignment of the mirrors was also developed. The focusing properties for 10-keV X-rays were evaluated with a wire-scanning method. The focal beam size was determined to be 0.95 μm × 1.20 μm at the full width at half maximum. An increased power density of 1018 W/cm2 was achieved at the focal point. These properties were confirmed to be in good agreement with the designed value.
A beamline for X-ray free electron laser (XFEL) has been developed at SACLA, SPring-8 Angstrom Compact free electron LAser. The beamline delivers and diagnoses an XFEL beam without degrading the beam ...quality. The transport optics are applicable in the range of 4–30 keV with a double-crystal monochromator or 4–15 keV with either of two double-mirror systems. A photon diagnostic system of the beamline monitors intensity, photon energy, center-of-mass position, and spatial profile in shot-by-shot and non-destructive manners.
We report a fabrication method of an ultrathin silicon crystal as a beam splitter for the hard x-ray regime based on the Bragg diffraction operated in the symmetric Bragg geometry, and evaluation ...results of crystalline perfection at SPring-8. A sub-10-μm thick Si(511) crystal was fabricated with a reactive dry etching method using atmospheric-pressure plasma. Following the evaluation of topography and diffractometry, the crystal was found to be strain-free, and capable of splitting a monochromatic x-ray beam into two branches with almost 1:1 splitting ratio.
We evaluated the ablation threshold of silicon and synthetic fused silica, which are widely used as optical substrates such as those in X-ray mirrors. A focusing XFEL beam with a beam size of ...approximately 1 μm at a photon energy of 10 keV was used. We confirmed that the ablation thresholds of these materials, which were 0.8 μJ/μm2 for the silicon and 4 μJ/μm2 for the synthetic fused silica, approximately agreed with the melting dose.
Phytochromes are red/far-red light photoreceptors in bacteria to plants, which elicit a variety of important physiological responses. They display a reversible photocycle between the resting Pr state ...and the light-activated Pfr state. Light signals are transduced as structural change through the entire protein to modulate its activity. It is unknown how the Pr-to-Pfr interconversion occurs, as the structure of intermediates remains notoriously elusive. Here, we present short-lived crystal structures of the photosensory core modules of the bacteriophytochrome from myxobacterium Stigmatella aurantiaca captured by an X-ray free electron laser 5 ns and 33 ms after light illumination of the Pr state. We observe large structural displacements of the covalently bound bilin chromophore, which trigger a bifurcated signaling pathway that extends through the entire protein. The snapshots show with atomic precision how the signal progresses from the chromophore, explaining how plants, bacteria, and fungi sense red light.
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•Successful TR-SFX experiments were conducted on a myxobacterial phytochrome at SACLA•The Z-to-E isomerization of the biliverdin chromophore is observed at 5 ns and 33 ms•Structural changes extend through the entire phytochrome at both time delays
Phytochromes are the molecular eyes of plants and bacteria that regulate cellular response to light, an essential environmental signal. Carrillo, Pandey et al. successfully investigate these structural changes in real time and with extreme magnification at one of the strongest X-ray sources, the free electron laser SACLA in Japan.
The successful lasing and operation of the LCLS hard X-ray FEL has brought tremendous interest to the user community spanning a wide range of scientific disciplines including physics, chemistry, ...structural biology, and material science. It created demand on beam time that is often left unfulfilled. Here we report experimental measurements of ultra-thin silicon single-crystal membranes for potentially beam-sharing the LCLS beam. The samples included the (111), (220), and (400) orientations with thicknesses ranging from 5 to 20 μm. Both high-resolution rocking curves and topographic data were first obtained using synchrotron X-rays, demonstrating near ideal diffraction qualities. Subsequent tests using the full LCLS beam revealed lattice distortions from beam-induced membrane vibrations, which were shown to be effectively reduced by ambient air and smaller membrane dimensions. High diffraction quality thin-diamonds in the (111) orientation are also being pursued as a parallel effort. Both approaches are paving a way for a practical beam-sharing implementation at LCLS in the near future.
We have investigated multiphoton multiple ionization of Ar and Xe atoms irradiated by intense X-ray pulses using the new X-ray free electron laser facility SACLA. The experimental results are ...compared with theoretical results.
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