An extraction algorithm for core-level excitations in non-resonant inelastic X-ray scattering spectra

Sternemann, H.; Sternemann, Christian; Seidler, Gerald T.; Fister, Timothy T.; Sakko, Arto; Tolan, Metin

doi:10.1107/s0909049508001696

Cited by 49 publications

(45 citation statements)

References 33 publications

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“…Incident energy selectivity was accomplished with a double-bounce Si(111) monochromator, providing ~1.4 eV FWHM energy resolution. Spectrometer operation and performance were consistent with previous work [21,25,31,32]. EELS measurements were acquired using a TITAN electron microscope with a monochromatic electron.…”

Section: Methodsmentioning

confidence: 89%

Core and shallow-cored- tof-shell excitations in rare-earth metals

et al. 2011

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We report on the results of probing the light lanthanide metals Ce, Pr, and Nd with inelastic x-ray and electron scattering. Transmission electron microscope-based electron spectroscopy and nonresonant inelastic x-ray scattering are shown to be in a high degree of accord, and here serve as complementary probes of electronic structure. The high resolution and high signal-to-noise electron technique allows for the measurement of the complex and subtle excitation spectra in the lanthanide metals, validating the applicability of the screened trivalent atomic model used for these materials. In addition, the momentum transfer dependence of the x-ray scattering is extracted and compared against atomic calculations for the most tightly bound excitonic resonances, which provides a direct test of the predicted atomic radial wave functions.

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Section: Methodsmentioning

confidence: 89%

Core and shallow-cored- tof-shell excitations in rare-earth metals

et al. 2011

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“…Final XRS spectra were normalized to the integral intensity between 531 eV and 555 eV. Details of the data processing and analysis can be found in a study by Sternemann et al (58). Because we could observe the sample during the experiment through a microscope, we can exclude any sample damage due to the X-ray exposure.…”

Section: Methodsmentioning

confidence: 99%

Microscopic structure of water at elevated pressures and temperatures

Sahle

Sternemann

Schmidt

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

128

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We report on the microscopic structure of water at sub-and supercritical conditions studied using X-ray Raman spectroscopy, ab initio molecular dynamics simulations, and density functional theory. Systematic changes in the X-ray Raman spectra with increasing pressure and temperature are observed. Throughout the studied thermodynamic range, the experimental spectra can be interpreted with a structural model obtained from the molecular dynamics simulations. A spatial statistical analysis using Ripley's K-function shows that this model is homogeneous on the nanometer length scale. According to the simulations, distortions of the hydrogenbond network increase dramatically when temperature and pressure increase to the supercritical regime. In particular, the average number of hydrogen bonds per molecule decreases to ≈0.6 at 600°C and p = 134 MPa.supercritical water | water structure | X-ray scattering | X-ray scattering spectroscopy

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“…The separation of the XRS signal from the larger Compton background is a key experimental difficulty in all XRS measurements 16,27 . The valence Compton backgrounds are approximated by fitting the pre-edge data to standard Compton forms and using the low-q limit XRS form as a reference 26 .…”

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confidence: 99%

Exciton spectroscopy of hexagonal boron nitride using nonresonant x-ray Raman scattering

et al. 2008

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We report non-resonant x-ray Raman scattering (XRS) measurements from hexagonal boron nitride for transferred momentum from 2 to 9Å −1 along directions both in and out of the basal plane. A symmetry-based argument, together with real-space full multiple scattering calculations of the projected density of states in the spherical harmonics basis, reveals that a strong pre-edge feature is a dominantly Y10-type Frenkel exciton with no other s-, p-, or d -components. This conclusion is supported by a second, independent calculation of the q-dependent XRS cross-section based on the Bethe-Salpeter equation. The physics of low-energy photoelectrons in solids is a complex, many body problem 1 . All aspects of the electronic structure of the material must be taken into account 2,3 , including the interaction between the photoelectron and the complementary hole 3,4,5,6 . This latter effect allows for similar long-lived bound states in metals (generally called Fermi-edge singularities) 7 and in insulators (called excitons) 8 . As a canonical example of a many body problem in condensed matter physics, core-excitons are a topic of continuing interest 4,5,6 .The present synergy between steadily progressing ab initio theoretical treatments 2,3,9,10 and on-going improvements in instrumentation 11 in studies of nonresonant x-ray Raman scattering (XRS) shows a strong potential for rapid progress on this old problem 5,6 . XRS is the inelastic scattering of hard x-rays from bound electrons, and XRS studies have seen a recent explosion in the number and range of applications 5,6,11,12,13,14,15,16,17 . In comparison with q-resolved electron energy loss spectroscopy (EELS) 18 , XRS is more suited for bulk condensed matter systems 13 due to the large penetration length afforded by the relative high-energy incident and scattered photons. The measured q-dependent XRS provides direct information about multipole contributions to the dynamic structure factor S(q, ω) 5,6,14,15,16 . It can be directly compared with theoretical calculations of S(q, ω) 6,14,15,16 , and can in some cases be inverted to provide an experimental measure of the perturbed projected density of states (l -DOS) 10,19 , which can again be compared to theory.XRS has shown itself to be especially suitable for spectroscopy of the angular characteristics of core excitons at the near edge region. For example, XRS studies 5,6 on LiF and icosahedral B 4 C convincingly demonstrated s-, and p-type excitons at the F and B K-edges, respectively, which can be attributed to atoms located at a center of inversion symmetry of the unit cell with parity a good quantum number for the final states 6 . Here, we demonstrate that for some systems one can learn not only the ∆l selection rule for the exciton but also a full description of its angular characteristics in terms of spherical harmonics, Y lm .We present measurements of the q-dependent XRS of hexagonal boron nitride (h-BN), an anisotropic system with all atoms sitting at positions with reflection symmetry to the basal plane (Figure 1,...

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An extraction algorithm for core-level excitations in non-resonant inelastic X-ray scattering spectra

Cited by 49 publications

References 33 publications

Core and shallow-cored- tof-shell excitations in rare-earth metals

Core and shallow-cored- tof-shell excitations in rare-earth metals

Microscopic structure of water at elevated pressures and temperatures

Exciton spectroscopy of hexagonal boron nitride using nonresonant x-ray Raman scattering

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