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Subject: Electronic excitation × WGL Institute: IFWD ×

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Now showing 1 - 2 of 2
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    Loss spectroscopy of molecular solids: Combining experiment and theory
    (Milton Park : Taylor & Francis, 2013) Roth, Friedrich; Cudazzo, Pierluigi; Mahns, Benjamin; Gatti, Matteo; Bauer, Johannes; Hampel, Silke; Nohr, Markus; Berger, Helmuth; Knupfer, Martin; Rubio, Angel
    The nature of the lowest-energy electronic excitations in prototypical molecular solids is studied here in detail by combining electron energy loss spectroscopy (EELS) experiments and state-of-the-art many-body calculations based on the Bethe–Salpeter equation. From a detailed comparison of the spectra in picene, coronene and tetracene we generally find a good agreement between theory and experiment, with an upshift of the main features of the calculated spectrum of 0.1–0.2 eV, which can be considered the error bar of the calculation. We focus on the anisotropy of the spectra, which illustrates the complexity of this class of materials, showing a high sensitivity with respect to the three-dimensional packing of the molecular units in the crystal. The differences between the measured and the calculated spectra are explained in terms of the small differences between the crystal structures of the measured samples and the structural model used in the calculations. Finally, we discuss the role played by the different electron–hole interactions in the spectra. We thus demonstrate that the combination of highly accurate experimental EELS and theoretical analysis is a powerful tool to elucidate and understand the electronic properties of molecular solids.
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    Resonant inelastic x-ray incarnation of Young’s double-slit experiment
    (Washington : American Association for the Advancement of Science (A A A S), 2019) Revelli, A.; Moretti, Sala, M.; Monaco, G.; Becker, P.; Bohatý, L.; Hermanns, M.; Koethe, T.C.; Fröhlich, T.; Warzanowski, P.; Lorenz, T.; Streltsov, S.V.; van Loosdrecht, P.H.M.; Khomskii, D.I.; van den Brink, J.; Grüninger, M.
    Young’s archetypal double-slit experiment forms the basis for modern diffraction techniques: The elastic scattering of waves yields an interference pattern that captures the real-space structure. Here, we report on an inelastic incarnation of Young’s experiment and demonstrate that resonant inelastic x-ray scattering (RIXS) measures interference patterns, which reveal the symmetry and character of electronic excited states in the same way as elastic scattering does for the ground state. A prototypical example is provided by the quasi-molecular electronic structure of insulating Ba 3 CeIr 2 O 9 with structural Ir dimers and strong spin-orbit coupling. The double “slits” in this resonant experiment are the highly localized core levels of the two Ir atoms within a dimer. The clear double-slit-type sinusoidal interference patterns that we observe allow us to characterize the electronic excitations, demonstrating the power of RIXS interferometry to unravel the electronic structure of solids containing, e.g., dimers, trimers, ladders, or other superstructures.