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• Delicate images can be retrieved from tarnished daguerreotypes by tracking the Hg Lα XRF excited with a focused synchrotron X-ray beam at energy just above the Hg L3 -edge if the bulk of the image particles remains intact. Surface corrosion is not an issue. • While the risk of radiation damage is low, ultra bright X-ray can produce radiation damage in scattered spots, an upper bound of flux tolerance has been established. • Image can also be retrieved with tender X-rays (2.5–7 keV) using Ag L α and Hg Mα XRF; the shallow penetration depth of tender X-rays minimizes background. • Tender X-ray imaging in a high vacuum provides the added advantage of measuring the surface sensitive total electron yield and the bulk sensitive fluorescence yield, which in turn can be used for micro-spectroscopy and surface corrosion analysis. We report recent observations using a synchrotron X-ray micro-beam to retrieve images from tarnished 19th century daguerreotypes. We confirm that high quality image can always be retrieved from tarnished plates using Hg L α XRF as long as the bulk of the image particles and their distribution remains intact. We also report results from using tunable tender X-rays (2 - 7 keV) to conduct imaging in high vacuum at energy above the Ag L-edge and the Hg M-edge, extracting images using Ag L α and Hg M α , respectively among others (e.g., S to track corrosion). Images obtained with the surface sensitive total electron yield (TEY) and the bulk sensitive fluorescence yield (FLY) as well as corresponding micro-XANES are reported. Flux tolerance to high intensity X-beam is also explored. These results and their implications for cultural heritage research are discussed. [ABSTRACT FROM AUTHOR]

As the first experiment at BL10U in NanoTerasu, tender X-ray ptychographic coherent diffraction imaging (PCDI) was conducted using a photon energy of 3.5 keV. The ptychographic diffraction patterns from a 200 nm thick Ta test chart and a micrometer-sized particle of sulfurized polymer were collected. Subsequently, phase images were reconstructed with resolutions of sub-20 nm and sub-50 nm, respectively. In the near future, tender X-ray PCDI with sub-10 nm resolution is anticipated to potentially revolutionize the visualization of nanoscale structures and chemical states in various functional materials composed of light elements.

Understanding the ultrafast dynamics of molecules is of fundamental importance. Time-resolved X-ray absorption spectroscopy (TR-XAS) is a powerful spectroscopic technique for unveiling the time-dependent structural and electronic information of molecules that has been widely applied in various fields. Herein, the design and technical achievement of a newly developed experimental apparatus for TR-XAS measurements in the tender X-ray range with X-ray free-electron lasers (XFELs) at the Pohang Accelerator Laboratory XFEL (PAL-XFEL) are described. Femtosecond TR-XAS measurements were conducted at the Ru L3-edge of well known photosensitizer tris(bipyridine)ruthenium(II) chloride ([Ru(bpy)3]2+) in water. The results indicate ultrafast photoinduced electron transfer from the Ru center to the ligand, which demonstrates that the newly designed setup is applicable for monitoring ultrafast reactions in the femtosecond domain.

The X-ray free-electron laser of the Pohang Accelerator Laboratory (PAL-XFEL) was opened to users in 2017. Since then, significant progress has been made in PAL-XFEL operation and beamline experiments. This includes increasing the FEL pulse energy, increasing the FEL photon energy, generating self-seeding FEL, and trials of two-color operation. In the beamline, new instruments or endstations have been added or are being prepared. Overall, beamline operation has been stabilized since its initiation, which has enabled excellent scientific results through efficient user experiments. In this paper, we describe details of the recent progress of the PAL-XFEL. [ABSTRACT FROM AUTHOR]

Understanding the ultrafast dynamics of molecules is of fundamental importance. Time‐resolved X‐ray absorption spectroscopy (TR‐XAS) is a powerful spectroscopic technique for unveiling the time‐dependent structural and electronic information of molecules that has been widely applied in various fields. Herein, the design and technical achievement of a newly developed experimental apparatus for TR‐XAS measurements in the tender X‐ray range with X‐ray free‐electron lasers (XFELs) at the Pohang Accelerator Laboratory XFEL (PAL‐XFEL) are described. Femtosecond TR‐XAS measurements were conducted at the Ru L3‐edge of well known photosensitizer tris(bipyridine)ruthenium(II) chloride ([Ru(bpy)3]2+) in water. The results indicate ultrafast photoinduced electron transfer from the Ru center to the ligand, which demonstrates that the newly designed setup is applicable for monitoring ultrafast reactions in the femtosecond domain. [ABSTRACT FROM AUTHOR]

Donor–acceptor (D–A) type semiconducting polymers have shown great potential for the application of deformable and stretchable electronics in recent decades. However, due to their heterogeneous structure with rigid backbones and long solubilizing side chains, the fundamental understanding of their molecular picture upon mechanical deformation still lacks investigation. Here, the molecular orientation of diketopyrrolopyrrole (DPP)‐based D–A polymer thin films is probed under tensile deformation via both experimental measurements and molecular modeling. The detailed morphological analysis demonstrates highly aligned polymer crystallites upon deformation, while the degree of backbone alignment is limited within the crystalline domain. Besides, the aromatic ring on polymer backbones rotates parallel to the strain direction despite the relatively low overall chain anisotropy. The effect of side‐chain length on the DPP chain alignment is observed to be less noticeable. These observations are distinct from traditional linear‐chain semicrystalline polymers like polyethylene due to distinct characteristics of backbone/side‐chain combination and the crystallographic characteristics in DPP polymers. Furthermore, a stable and isotropic charge carrier mobility is obtained from fabricated organic field‐effect transistors. This study deconvolutes the alignment of different components within the thin‐film microstructure and highlights that crystallite rotation and chain slippage are the primary deformation mechanisms for semiconducting polymers. [ABSTRACT FROM AUTHOR]

X‐SPEC is a high‐flux spectroscopy beamline at the KIT (Karlsruhe Institute of Technology) Synchrotron for electron and X‐ray spectroscopy featuring a wide photon energy range. The beamline is equipped with a permanent magnet undulator with two magnetic structures of different period lengths, a focusing variable‐line‐space plane‐grating monochromator, a double‐crystal monochromator and three Kirkpatrick–Baez mirror pairs. By selectively moving these elements in or out of the beam, X‐SPEC is capable of covering an energy range from 70 eV up to 15 keV. The flux of the beamline is maximized by optimizing the magnetic design of the undulator, minimizing the number of optical elements and optimizing their parameters. The beam can be focused into two experimental stations while maintaining the same spot position throughout the entire energy range. The first experimental station is optimized for measuring solid samples under ultra‐high‐vacuum conditions, while the second experimental station allows in situ and operando studies under ambient conditions. Measurement techniques include X‐ray absorption spectroscopy (XAS), extended X‐ray absorption fine structure (EXAFS), photoelectron spectroscopy (PES) and hard X‐ray PES (HAXPES), as well as X‐ray emission spectroscopy (XES) and resonant inelastic X‐ray scattering (RIXS). [ABSTRACT FROM AUTHOR]

Chirality is an essential research topic in material science, especially in soft materials including liquid crystals, polymers and biomaterials. There have been many discussions about chiral structures since people discovered and studied this particular property. Yet, due to the lack of effective characterization methods, many questions on helical structures of chiral materials remain unsolved. Here, we review recent applications of resonant soft (RSoXS) and tender resonant X-ray scattering (TReXS) on chirality study in soft materials, with a focus on liquid crystals phases. In the end, a perspective is presented on the potential applications and future improvements of resonant scattering.

The X-ray free-electron laser of the Pohang Accelerator Laboratory (PAL-XFEL) was opened to users in 2017. Since then, significant progress has been made in PAL-XFEL operation and beamline experiments. This includes increasing the FEL pulse energy, increasing the FEL photon energy, generating self-seeding FEL, and trials of two-color operation. In the beamline, new instruments or endstations have been added or are being prepared. Overall, beamline operation has been stabilized since its initiation, which has enabled excellent scientific results through efficient user experiments. In this paper, we describe details of the recent progress of the PAL-XFEL.

• High line density MLLG was simulated and proposed to improve the X-ray spectral resolution with high efficiency. • 3000-5000 l/mm MLLG can reach 40 times higher efficiency than the single-layer coated grating in the tender X-ray range. • A 3000 l/mm MLLG was experimentally demonstrated for the first time, showing a high efficiency of 54.5% at 4.4 keV. • The other 3000 l/mm MLLG was demonstrated with a large C ff factor of 4.3 and 23.1% efficiency at 4 keV. Driven by the demand of high efficiency and high resolution monochromators and spectrometers in the tender X-ray range, high line density multilayer coated laminar gratings (MLLG) were designed, manufactured, and analyzed. Theoretical simulations displayed that a 5000 l/mm MLLG could realize high resolution at 3 keV and 40 times higher diffraction efficiency than the single-layer coated grating. For the first demonstration of the high line density MLLGs, two 3000 l/mm laminar gratings were fabricated and coated by Cr/C multilayers with different periodic thicknesses to achieve high efficiency (HE) and high resolution (HR) performance. For MLLG-HE, a maximum efficiency of 54.5% was achieved at 4.4 keV. For MLLG-HR, relatively high efficiency of 23.1%–38.6% were demonstrated with much stronger asymmetric diffraction in 2–4 keV, which can significantly increase the energy resolution of the system. [ABSTRACT FROM AUTHOR]

An optical design study of a beamline proposed for the 3 GeV synchrotron radiation facility, the Shenzhen Light Source, is described. The beamline was designed to cover an energy range from 2.0 to 20 keV with two experimental station, one for X-ray absorption spectroscopy (XAS) experiments and the other for X-ray photon correlation spectroscopy (XPCS) experiments. A 4 m planar undulator with a relatively short magnetic period (20 mm) was used as the radiation source. Horizontally and vertically focusing mirrors separately focus the source along the horizontal and vertical directions, respectively, thus enhancing the flexibility of the beamline. The focus point was employed as the secondary source, and a pair of KB mirrors were used to achieve a near-circular focus spot of about 4. 5 μ m × 4. 5 μ m. A Si(111) DCM was selected to produce the monochromatic light that covers the 2.0–20 keV energy range. When the photon energy is lower than 10 keV, the energy resolution can be better than 1.47 × 10−4 and the total flux is larger than 1 × 1014 photons/s. The longitudinal coherence length is in a few μ m range. With aperture size adjustment, the transverse coherence length at the sample position is approximately 3 μ m and the coherent flux is up to 1012 phs/s for the photon energy around 2.5 keV. This excellent coherence performance can be applied for the purpose of X-ray photon correlation spectroscopy related experiments. [ABSTRACT FROM AUTHOR]