Soft X-ray Synchrotron Radiation Research Articles

Synchrotron radiation soft X-ray microscopy and low energy X-ray fluorescence to reveal elemental changes in spermatozoa treated with photobiomodulation therapy.

Male infertility is a worldwide clinical issue that increases the number of couples resorting to assisted reproductive technologies (ARTs) to achieve pregnancy. Photobiomodulation therapy (PBMT) is a promising technique that can biostimulate cells and tissues and it is currently successfully employed to enhance the sperm motility in vitro. Nevertheless, its use has been so far restricted to the research field. In the present work, we exploited two PBMT protocols at an 800 nm wavelength on sperm derived from infertile individuals, detecting an increase in sperm motility 1 hour after irradiation. Moreover, in order to add new information about the molecular effect of PBMT, the content of some light elements was evaluated using high resolution X-ray fluorescence imaging. Interestingly, an increase in Na content was detected in the irradiated samples, possibly suggesting a role of this element in sperm motility; indeed, a low Na content was previously correlated with a poor sperm quality, low semen volume, and modest fertilization rate. Amplifying the knowledge of PBMT in the ART field will expedite the translational potentiality of the PBMT use in clinical settings.

Pristine and oxidised Ag-nanoparticles on free-standing graphene as explored by X-ray photoelectron and Auger spectroscopy

Silver nanoparticles with a mean diameter of 15 nm have been grown on free-standing graphene and explored by soft X-ray synchrotron radiation using the ESCAmicroscopy beamline at Elettra. In particular, the 3d core orbitals and valence band (4d/5 s) of pristine and plasma-oxidised Ag-nanoparticles have been investigated by X-ray photoelectron spectroscopy (XPS), X-ray induced valence band photoemission, and MNN Auger spectroscopy. The X-ray spectra of the pristine Ag-nanoparticles, i.e. XPS, Auger and UPS spectra, are very similar to these of the metallic Ag-bulk film while the spectra of the oxidised Ag-nanoparticles exhibit distinct differences with respect to the oxidised Ag-bulk film. This is inferred from a larger valence band width, an extended valence band photoemission intensity nearly up to the Fermi level of the bulk metal, a smaller two-hole Coulomb correlation energy and a rather bulk-like Auger spectrum. We interpret this as to result from a shell-like composition of the Ag-nanoparticles with a thin passivating oxide layer and an inner metallic core. Moreover, the 3d photoemission peak of the oxidised nanoparticles is shifted to higher binding energy with respect to the bulk oxide peak. This is attributed not only to an XPS chemical shift but also to an additional final state Coulomb charging according to the electrostatic liquid drop model. Comparing the core binding energy shift of Ag-nanoparticles with the electrostatic potential of a spherical compact particle and a flat nanoislands a morphology transformation of the oxidised nanoparticles from 3D to 2D is obvious in the size range 5–15 nm.

Applications of synchrotron radiation soft X-ray spectroscopies in the studies of surfaces and interfaces of functional materials

Applications of synchrotron radiation soft X-ray spectroscopies in the studies of surfaces and interfaces of functional materials

Electronic Structure of UTe2 Studied by Photoelectron Spectroscopy

The electronic structure of the unconventional superconductor UTe2 was studied by resonant photoelectron spectroscopy (RPES) and angle-resolved photoelectron spectroscopy (ARPES) with soft X-ray synchrotron radiation. The partial U 5f density of states of UTe2 were imaged by the U 4d–5f RPES and it was found that the U 5f state has an itinerant character, but there exists an incoherent peak due to the strong electron correlation effects. Furthermore, an anomalous admixture of the U 5f states into the Te 5p bands was observed at a higher binding energy, which cannot be explained by band structure calculations. On the other hand, the band structure of UTe2 was obtained by ARPES and its overall band structure were mostly explained by band structure calculations. These results suggest that the U 5f states of UTe2 have itinerant but strongly-correlated nature with enhanced hybridization with the Te 5p states.

Inspecting adhesion and cohesion of protectives and consolidants in sandstones of architectural heritage by X-ray microscopy methods

An innovative set-up of synchrotron radiation soft X-ray Fluorescence was applied at the TwinMic beamline (Elettra Sincrotrone Trieste) to test the potential of the method in investigating the interaction between protectives and consolidants with sandstone substrates. To this purpose, products developed in the framework of the EU-funded Nano-Cathedral Project (grant agreement No 646178) were studied through chemical mapping of sandstone cross sections with the aim of inspecting the distribution and the adhesion/cohesion ability of the products. The paper illustrates the obtained results, also in combination with SEM-EDS imaging, paying special attention to the experimental challenges encountered in the use of the TwinMic set-up. Even though the TwinMic microscope normally works in transmission mode to focus the microprobe on the sample, we successfully managed to scan thick (1 mm) samples in reflection mode, thus showing the potential of this technique for the investigation of samples that cannot be easily prepared as thin (≤1 μm) cross sections.

A coincidence velocity map imaging spectrometer for ions and high-energy electrons to study inner-shell photoionization of gas-phase molecules.

We report on the design and performance of a double-sided coincidence velocity map imaging spectrometer optimized for electron-ion and ion-ion coincidence experiments studying inner-shell photoionization of gas-phase molecules with soft X-ray synchrotron radiation. The apparatus employs two microchannel plate detectors equipped with delay-line anodes for coincident, time- and position-resolved detection of photoelectrons and Auger electrons with kinetic energies up to 300 eV on one side of the spectrometer and photoions up to 25 eV per unit charge on the opposite side. We demonstrate its capabilities by measuring valence photoelectrons and ion spectra of neon and nitrogen and by studying channel-resolved photoelectron and Auger spectra along with fragment-ion momentum correlations for chlorine 2p inner-shell ionization of cis- and trans-1,2-dichloroethene.

NOVEL ANALYTICAL STUDY FOR REACTION INTERMEDIATES IN THE PRIMARY RADIATION INTERACTION OF DNA USING A SYNCHROTRON RADIATION-INDUCED LUMINESCENCE SPECTROSCOPY

To identify the precise molecular processes to induce DNA lesions, we attempt a novel spectroscopy of X-ray induced luminescence (XIL) using soft X-ray synchrotron radiation, which is a non-destructive analysis of the reaction intermediates in the elementary reaction pathway of damage induction and self-organized restoration. Using a liquid micro-jet technique to introduce aqueous samples in a vacuum chamber, we measure UV-visible luminescence from nucleotide solution as a function of the soft X-ray energy from the nitrogen to oxygen K-edge region. The XIL intensities for the nucleotide solutions are significantly enhanced in the soft X-ray region (410-530 eV) which is ascribed to the K-shell excitation/ionization of nitrogen atoms in the nucleobases. Furthermore, the XIL spectra do not show any signature of X-ray absorption near-edge structure (XANES) of the nucleobases. This is because the luminescence intensities collected from the integral area of the micro-jet only reflect the quantum yield of luminescence of the absorbed X-ray into UV-visible light irrespective of the absorption cross sections, i.e. of XANES. Thus the present result is the first evidence of luminescence as a result of X-ray absorption of aqueous nucleotides.

Fortune is Unpredictable and Changeable, Especially for Soft X-ray Synchrotron Radiation Researcher

Fortune is Unpredictable and Changeable, Especially for Soft X-ray Synchrotron Radiation Researcher

Valence and Core-Level X-ray Photoelectron Spectroscopy of a Liquid Ammonia Microjet.

Photoelectron spectroscopy of microjets expanded into vacuum allows access to orbital energies for solute or solvent molecules in the liquid phase. Microjets of water, acetonitrile and alcohols have previously been studied; however, it has been unclear whether jets of low temperature molecular solvents could be realized. Here we demonstrate a stable 20 μm jet of liquid ammonia (−60 °C) in a vacuum, which we use to record both valence and core-level band photoelectron spectra using soft X-ray synchrotron radiation. Significant shifts from isolated ammonia in the gas-phase are observed, as is the liquid-phase photoelectron angular anisotropy. Comparisons with spectra of ammonia in clusters and the solid phase, as well as spectra for water in various phases potentially reveal how hydrogen bonding is reflected in the condensed phase electronic structure.

Cs 吸着バーミキュライトの軟 X 線放射光光電子分光

Cs 吸着バーミキュライトの軟 X 線放射光光電子分光

Normal and resonant Auger spectroscopy of isocyanic acid, HNCO.

In this paper, we investigate HNCO by resonant and nonresonant Auger electron spectroscopy at the K-edges of carbon, nitrogen, and oxygen, employing soft X-ray synchrotron radiation. In comparison with the isosteric but linear CO2 molecule, spectra of the bent HNCO molecule are similar but more complex due to its reduced symmetry, wherein the degeneracy of the π-orbitals is lifted. Resonant Auger electron spectra are presented at different photon energies over the first core-excited 1s → 10a' resonance. All Auger electron spectra are assigned based on ab initio configuration interaction computations combined with the one-center approximation for Auger intensities and moment theory to consider vibrational motion. The calculated spectra were scaled by a newly introduced energy scaling factor, and generally, good agreement is found between experiment and theory for normal as well as resonant Auger electron spectra. A comparison of resonant Auger spectra with nonresonant Auger structures shows a slight broadening as well as a shift of the former spectra between -8 and -9 eV due to the spectating electron. Since HNCO is a small molecule and contains the four most abundant atoms of organic molecules, the reported Auger electron decay spectra will provide a benchmark for further theoretical approaches in the computation of core electron spectra.

Circular Dichroism in Fluorescence Emission Following the C 1s→π* Excitation and Resonant Auger Decay of Carbon Monoxide.

Dichroism in angle-resolved spectra of circularly polarized fluorescence from freely-rotating CO molecules was studied experimentally and theoretically. For this purpose, carbon monoxide in the gas phase was exposed to circularly polarized soft X-ray synchrotron radiation. The photon energy was tuned across the C 1s→π* resonant excitation, which decayed via the participator Auger transition into the CO+ A 2Π state. The dichroic parameter β1 of the subsequent CO+ (A 2Π → X 2Σ+) visible fluorescence was measured by photon-induced fluorescence spectroscopy. Present experimental results are explained with the ab initio electronic structure and dynamics calculations performed by the single center method. Our results confirm the possibility to perform partial wave analysis of the emitted photoelectrons in closed-shell molecules.

Quantitative ptychographic bio-imaging in the water window.

Coherent X-ray ptychography is a tool for highly dose efficient lensless nano-imaging of biological samples. We have used partially coherent soft X-ray synchrotron radiation to obtain a quantitative image of a laterally extended, dried, and unstained fibroblast cell by ptychography. We used data with and without a beam stop that allowed us to measure coherent diffraction with a high-dynamic range of 1.7·106. As a quantitative result, we obtained the refractive index values for two regions of the cell with respect to a reference area. Due to the photon energy in the water window we obtained an extremely high contrast of 53% at 71 nm half-period resolution. The dose applied in our experiment was 9.5·104 Gy and is well below the radiation damage threshold. The concept for dynamic range improvement for low dynamic range detectors with a beam stop opens the path for high resolution nano-imaging of a variety of samples including cryo-preserved, hydrated and unstained biological cells.

Adsorption and photolysis of trimethyl acetate on TiO2(B)(001) studied with synchrotron radiation core level photoelectron spectroscopy

We present a synchrotron radiation photoelectron spectroscopy study of the adsorption and photooxidation of trimethyl acetate (TMA) on TiO2(B)(001). The TiO2(B)(001) substrate was realized in the form of 2 nm thick film on Au(111). The TMA species adopt the bidentate bonding configuration, as expected for carboxylic acids on TiO2, but cannot coordinate to all surface Ti ions due to steric hindrance. The proposed arrangement of the TMA species thus allows for the formation of an overlayer with a (2 × 1) periodicity. The thermal stability is found to be comparable to that on rutile (110) although the results indicate differences in the threshold for the TMA + H→TMAA reaction. Photolysis using both ultraviolet (UV) light and soft x-ray synchrotron radiation (SR) was studied and compared to the reaction on the reduced rutile (110) surface. A kinetic analysis suggests that the photoreaction rate for TMA on the TiO2(B) thin film is initially two times faster than that on the reduced rutile TiO2(110) surface. The higher activity of the TiO2(B) film is assigned to a reduced influence from surplus electrons associated with reduced Ti species, thereby decreasing the probability for hole-annihilation at high TMA coverage.

Soft X-ray induced ultraviolet fluorescence emission from bulk and interface of a liquid water microjet

SynopsisTremendous progress has been made in the research on the structure and dynamics of liquids due to the development of advanced experimental techniques such as liquid microjets, enabling investigations on volatile samples in ultrahigh vacuum environments. The spectroscopy of charged particles, e.g. photoelectron or Auger electron spectroscopy on liquids, is an established field by now. Here, we report on the successful application of a fluorescence spectrometer to measure optical emission spectra from liquids irradiated with soft X-ray synchrotron radiation.

Development of optical choppers for time-resolved measurements at soft X-ray synchrotron radiation beamlines.

Two types of optical choppers for time-resolved measurements at synchrotron radiation soft X-ray beamlines have been developed. One type uses an air-spindle-type rotation mechanism with a two-stage differential pumping system to maintain the ultra-high vacuum of the X-ray beamline, and the other uses a magnetic bearing. Both can be installed at the soft X-ray beamlines at SPring-8, greatly improving the accessibility of pump-and-probe spectroscopy. The combination of X-ray chopper and pump-and-probe photoemission electron microscope at SPring-8 provides drastic improvements in signal-to-noise ratio and resolution compared with techniques using high-voltage gating of channel plate detectors. The choppers have the capability to be used not only at synchrotron radiation facilities but also at other types of soft X-ray and VUV beamlines.

Soft X-ray synchrotron radiation spectroscopy study of rare-earth chalcogenide charge-density wave compounds

The electronic structures of the layered rare-earth chalcogenide compounds of CeTe2, PrTe2, and PrTe3, which have the charge-density wave (CDW) transition and possibly the chiral transition, have been investigated by employing soft X-ray absorption spectroscopy (XAS) and angle-resolved photoemission spectroscopy (ARPES). R 3d XAS measurements show that the valence states of Ce and Pr ions are nearly trivalent in all the compounds. Similar band dispersions are observed in their measured ARPES data, but with the band positions in PrTe3 being shifted up in energy compared to those in CeTe2 and PrTe2. These findings suggest that their Te 5p band structures are determined mainly by the 2D interactions in the Te(2)/Te(3) sheets, but with a larger number of holes in the Te 5p bands in PrTe3 than in CeTe2 and PrTe2. The measured constant energy maps of CeTe2, PrTe2, and PrTe3 for high binding energies are similar to one another, reflecting the Te 5p band structures of the Te(2)/Te(3) square nets. In contrast, the Fermi surfaces (FSs) of CeTe2 and PrTe3 exhibit extra features, different from the FS of the ideal Te(2)/Te(3) square nets, which arise from the CDW-induced FS reconstruction in the Te(2)/Te(3) sheets.

Ultrafast molecular dynamics of dissociative ionization in OCS probed by soft x-ray synchrotron radiation

Soft x-rays (90–173 eV) from the 3rd generation Canadian Light Source have been used in conjunction with a multi coincidence time and position sensitive detection apparatus to observe the dissociative ionization of OCS. By varying the x-ray energy we can compare dynamics from direct and Auger ionization processes, and access ionization channels which result in two or three body breakup, from 2+ to 4+ ionization states. We make several new observations for the 3+ state such as kinetic energy release limited by photon energy, and using Dalitz plots we can see evidence of timescale effects between the direct and Auger ionization process for the first time. Finally, using Dalitz plots for OCS4+ we observe for the first time that breakup involving an O2+ ion can only proceed from out of equilibrium nuclear arrangement for S(2p) Auger ionization.

Electronic Structures of Uranium Compounds Studied by Soft X-ray Photoelectron Spectroscopy

The electronic structures of uranium-based compounds have been studied by photoelectron spectroscopy with soft X-ray synchrotron radiation. Angle-resolved photoelectron spectroscopy with soft X-rays has made it possible to directly observe their bulk band structures and Fermi surfaces. It has been shown that the band structures and Fermi surfaces of itinerant compounds such as UB2, UN, and UFeGa5 are quantitatively described by a band-structure calculation treating all U 5f electrons as itinerant. Furthermore, the overall electronic structures of heavy-fermion compounds such as UPd2Al3, UNi2Al3, and URu2Si2 are also explained by a band-structure calculation, although some disagreements exist, which might originate from the electron correlation effect. This suggests that the itinerant description of U 5f states is an appropriate starting point for the description of their electronic structures. The situation is similar for ferromagnetic superconductors such as UGe2, URhGe, UCoGe, and UIr, although the comp...

NEXAFS N K-edge study of the bonding structure on Al/Si doped sputtered CrN coatings

Chromium nitride (CrN)-based materials display broad applications as protective coatings for automotive, power generation and aerospace industries, in which surfaces are often subjected to wear and corrosion. By using an appropriate choice of dopant, one can further increase the mechanical hardness, corrosion and oxidation resistance of these coatings. In order to identify the effect of dopants on the structural evolution and surface electronic properties of CrN coatings, Cr1-z(Al/Si)zN coatings were prepared by magnetron sputtering and then characterized via X-ray diffraction (XRD) and soft X-ray synchrotron radiation Near-edge X-ray Absorption Fine Structure (NEXAFS) studies around N K-edge. Higher degree of crystallinity of the coatings were identified through XRD studies. The bonding structure, of the doped CrN coating, was analyzed by Near-edge X-ray Absorption Fine Structure (NEXAFS) measurements performed around the N K-edge (390–450 eV) in the Auger electron yield (AEY) and total fluorescence yield (TFY) modes. NEXAFS analysis revealed Cr3d(Al3p/Si3p)N2p hybridizations in Cr1-z(Al/Si)zN compositions and complex structure splitting via spin–orbit interaction of the Cr3d levels.