A compact von Hámos spectrometer for parallel X-ray Raman scattering and X-ray emission spectroscopy at ID20 of the European Synchrotron Radiation Facility.

A compact spectrometer for medium-resolution resonant and non-resonant X-ray emission spectroscopy in von Hámos geometry is described. The main motivation for the design and construction of the spectrometer is to allow for acquisition of non-resonant X-ray emission spectra while measuring non-resonant X-ray Raman scattering spectra at beamline ID20 of the European Synchrotron Radiation Facility. Technical details are provided and the performance and possible use of the spectrometer are demonstrated by presenting results of several X-ray spectroscopic methods on various compounds.

TEXS: in-vacuum tender X-ray emission spectrometer with 11 Johansson crystal analyzers.

The design and first results of a large-solid-angle X-ray emission spectrometer that is optimized for energies between 1.5 keV and 5.5 keV are presented.

A large-solid-angle X-ray Raman scattering spectrometer at ID20 of the European Synchrotron Radiation Facility.

An end-station for X-ray Raman scattering spectroscopy at beamline ID20 of the European Synchrotron Radiation Facility is described. This end-station is dedicated to the study of shallow core electronic excitations using non-resonant inelastic X-ray scattering. The spectrometer has 72 spherically bent analyzer crystals arranged in six modular groups of 12 analyzer crystals each for a combined maximum flexibility and large solid angle of detection.

High energy-resolution x-ray spectroscopy at ultra-high dilution with spherically bent crystal analyzers of 0.5 m radius.

We present the development, manufacturing, and performance of spherically bent crystal analyzers (SBCAs) of 100 mm diameter and 0.5 m bending radius. The elastic strain in the crystal wafer is partially released by a "strip-bent" method where the crystal wafer is cut into strips prior to the bending and the anodic bonding process.

Signature of a polyamorphic transition in the THz spectrum of vitreous GeO2.

The THz spectrum of density fluctuations, S(Q, ω), of vitreous GeO2 at ambient temperature was measured by inelastic x-ray scattering from ambient pressure up to pressures well beyond that of the known α-quartz to rutile polyamorphic (PA) transition. We observe significant differences in the spectral shape measured below and above the PA transition, in particular, in the 30-80 meV range. Guided by first-principle lattice dynamics calculations, we interpret the changes in the phonon dispersion as the evolution from a quartz-like to a rutile-like coordination.

Protonation Dynamics and Hydrogen Bonding in Aqueous Sulfuric Acid.

Hydration of sulfuric acid plays a key role in new-particle formation in the atmosphere. It has been recently proposed that proton dynamics is crucial in the stabilization of these clusters. One key question is how water molecules mediate proton transfer from sulfuric acid, and hence how the deprotonation state of the acid molecule behaves as a function concentration.

Improving the energy resolution of bent crystal X-ray spectrometers with position-sensitive detectors.

Wavelength-dispersive high-resolution X-ray spectrometers often employ elastically bent crystals for the wavelength analysis. In a preceding paper [Honkanen et al. (2014).

Temperature dependence of crystal field excitations in CuO.

We report a study on the temperature dependence of charge-neutral crystal field (dd) excitations in cupric oxide, using nonresonant inelastic x-ray scattering spectroscopy. Thanks to a very high-energy resolution (ΔE = 60 meV), we observe thermal effects on the dd excitation spectrum fine structure between temperatures of 10-320 K. The spectra broaden considerably with increasing temperature, consistently with an enhancement of the coupling between crystal field excitations and the temperature-dependent continuum of states above the band gap.

Crystal-field excitations in NiO under high pressure studied by resonant inelastic x-ray scattering.

We report a study on charge-neutral crystal-field (dd) excitations in NiO as a function of applied pressure up to 55 GPa, using resonant inelastic x-ray scattering spectroscopy at the Ni K edge. We find distinct signatures of the pressure-induced modifications to the 3d orbital energies as a function of pressure. These modifications are experimentally evidenced by a subtle splitting of the dd-excitation resonance energies.

Study on the reflectivity properties of spherically bent analyser crystals.

Theoretical and experimental studies are presented on properties of spherically bent analyser crystals for high-resolution X-ray spectrometry. A correction to the bent-crystal strain field owing to its finite surface area is derived. The results are used to explain the reflectivity curves and anisotropic properties of Si(660) and Si(553) analysers in near-backscattering geometry.

Direct tomography with chemical-bond contrast.

Three-dimensional (3D) X-ray imaging methods have advanced tremendously during recent years. Traditional tomography uses absorption as the contrast mechanism, but for many purposes its sensitivity is limited. The introduction of diffraction, small-angle scattering, refraction, and phase contrasts has increased the sensitivity, especially in materials composed of light elements (for example, carbon and oxygen).

The single particle dynamics of iodine in the Sachs-Teller regime: an inelastic x-ray scattering study.

The high frequency dynamics of liquid iodine has been investigated by deep inelastic x-ray scattering at exchanged wave-vectors (q) ranging from 2.5 to 15 Å(-1). The experimental data have been analyzed in the frame of the Sachs-Teller theory of the molecular spectrum while accounting for final state corrections to the lineshape.

Onset of the alpha-relaxation in the glass-forming solution LiCl-6H2O revealed by Brillouin scattering techniques.

We measured the dynamic structure factor of the liquid and glassy phases of the LiCl-6H(2)O solution by means of inelastic scattering of radiation in the visible, UV, and x-ray range, between 1 GHz and 10 THz, and by means of photon-correlation spectroscopy, between 0.01 Hz and 20 kHz. The measurements were performed in the temperature range between 353 and 80 K.

Multiple-element spectrometer for non-resonant inelastic X-ray spectroscopy of electronic excitations.

A multiple-analyser-crystal spectrometer for non-resonant inelastic X-ray scattering spectroscopy installed at beamline ID16 of the European Synchrotron Radiation Facility is presented. Nine analyser crystals with bending radii R = 1 m measure spectra for five different momentum transfer values simultaneously. Using a two-dimensional detector, the spectra given by all analysers can be treated individually.

Energy calibration of a high-resolution inelastic x-ray scattering spectrometer.

The energy scale of a triple-axis x-ray spectrometer with meV energy resolution based on perfect silicon crystal optics is calibrated, utilizing the most recent determination of the silicon lattice parameter and its thermal expansion coefficient and recording the dispersion of longitudinal acoustic and optical phonons in a diamond single crystal and the molecular vibration mode in liquid nitrogen. Comparison of the x-ray results with previous inelastic neutron and Raman scattering results as well as with ab initio phonon dispersion calculations yields an overall agreement better than 2%.

Zero sound mode in normal liquid 3He.

Inelastic x-ray scattering has been utilized to study the elementary excitations of normal liquid 3He at the temperature T=1.10+/-0.05 K and saturated vapor pressure in the wave vector range 0.

Bond-induced ergodicity breakdown in reactive mixtures.

We have studied by inelastic x-ray scattering, at wave vectors 1 nm < or =q< or =15 nm(-1), the high-frequency dynamics of epoxy-amine mixtures as the monomers irreversibly polymerize. We find that chemical bonding, while inducing molecular ordering on a mesoscopic length scale, also efficiently realizes the mechanism of dynamical arrest described by the mode-coupling theory, as manifested by a cusp singularity in the behavior of the nonergodicity factor as a function of the number of chemical bonds. These results confront positively the mode-coupling theory with a new control parameter.

Signatures of quantum behavior in the microscopic dynamics of liquid hydrogen and deuterium.

We discuss the microscopic dynamics and structure of liquid hydrogen and deuterium, as probed by inelastic x-ray scattering measurements. Samples are kept in corresponding thermodynamic conditions, at which classical systems are expected to exhibit the same dynamic and static responses. On the contrary, we observe clear differences revealing the onset of quantum deviations, both in the broadening of inelastic excitations and in the position of the first sharp diffraction peak.

Rubberlike dynamics in sulphur above the lambda-transition temperature.

The high-frequency acoustic dynamics of sulfur across the liquid-liquid, lambda transition has been studied using inelastic x-ray scattering. The combination of these high-frequency data with lower frequency, literature data indicates that liquid sulfur develops, in the high-temperature, polymeric solution phase, some characteristic features of a rubber. In particular, entanglement coupling among polymeric chains plays a relevant role in the dynamics of this liquid phase.

Improving the performance of high-resolution X-ray spectrometers with position-sensitive pixel detectors.

A dispersion-compensation method to remove the cube-size effect from the resolution function of diced analyzer crystals using a position-sensitive two-dimensional pixel detector is presented. For demonstration, a resolution of 23 meV was achieved with a spectrometer based on a 1 m Rowland circle and a diced Si(555) analyzer crystal in a near-backscattering geometry, with a Bragg angle of 88.5 degrees .

Ergodic to nonergodic transition in liquids with a local order: the case of m-toluidine.

The dynamic structure factor of m-toluidine has been measured by inelastic x-ray scattering in the mesoscopic Q range between 1 and 10 nm(-1), where a prepeak is revealed in the static structure factor resulting from the existence of hydrogen bonded, nanometer size clusters. Evidence is given of (i) a square-root cusp in the nonergodicity factor and of (ii) critical nonergodicity parameters which oscillate in phase with the static structure factor. These results demonstrate that local order in a liquid can coexist with the signatures of the ergodic to nonergodic transition predicted by the mode coupling theory for simple, dense liquids.

High-frequency longitudinal and transverse dynamics in water.

High-resolution, inelastic x-ray scattering measurements of the dynamic structure factor S (Q,omega) of liquid water have been performed for wave vectors Q between 4 and 30 nm(-1) in distinctly different thermodynamic conditions ( T=263-420 K ; at, or close to, ambient pressure and at P=2 kbar ). In agreement with previous inelastic x-ray and neutron studies, the presence of two inelastic contributions (one dispersing with Q and the other almost nondispersive) is confirmed. The study of their temperature and Q dependence provides strong support for a dynamics of liquid water controlled by the structural relaxation process.

Crystal-like nature of acoustic excitations in glassy ethanol.

We report on inelastic x-ray scattering experiments on crystalline and glassy phases of ethanol in order to directly compare the influence of disorder on high frequency acoustic excitations. We find that both the dispersion and the line-width of the longitudinal acoustic excitations in the glass are the same as in the polycrystal in the reciprocal space portion covering the 1st and 2nd Brillouin zones. The structural disorder is found to play little role apart from an intrinsic angular averaging, and the nature of these excitations must essentially be the same in both glass and poly crystal.