Static structure factor and electron correlation effects studied by inelastic x-ray scattering spectroscopy

Abstract

Anomalous electronic structure of ionic liquids determined by soft x-ray emission spectroscopy: Contributions from the cations and anions to the occupied electronic structure Inelastic x-ray scattering spectra of methanol, acetonitrile, benzene, and cyclohexane have been measured with 2 eV resolution for momentum transfer q between 0.69 and 2.77 a.u. using synchrotron radiation from the photon factory ͑PF͒ storage ring. By utilizing the Bethe sum rule, the spectra were brought onto an absolute scale, so that the static structure factor S(q) has been obtained. S(q) of these molecules has also been calculated at the single reference configuration interaction ͑CI͒ with several types of basis sets. A new formula is proposed to carry out spherical averaging accurately. It is concluded that the CI singles and doubles ͑CISD͒ treatment is necessary to predict correct S(q), and that an inclusion of polarization function influences S(q) significantly at this level. An addition of f functions also improves the agreement with the experiments. S(q)'s based on CISD wave functions are in good agreement with the experimental ones, in particular at large q.

Water Structure from Scattering Experiments and Simulation

“…90,91 The Compton scattering calculations using CISD and CCSD theories agree accurately with incoherent scattering from experiment on water 92 . A second source of systematic error in x-ray scattering is the commonly made assumption of the Debye approximation (Eq.…”

“…The primary problem in x-ray and neutron scattering is the removal of Compton or inelastic scattering, since only elastic scattering has meaningful structural content. X-ray scattering has benefited from technical advances at synchrotron facilities that allow the accurate measurement of the inelastic cross-section directly, so that we have a very good estimate of Compton scattering removal for water 92 . The removal of inelastic scattering from neutron data is more difficult by comparison because the measurement is not performed at constant Q, but instead the cross-section is measured at constant scattering angle θ.…”

Momentum dependence of π–π∗ excitations of benzene rings in condensed phases

“…For molecular liquids, optical absorption spectra below -7 eV [4] and Compton profiles [5] [6][7][8][9]. In particular, we have measured the equivalent of an absorption spectrum for liquid water with IXS [6,7] [8,9]. [9].…”

“…The loss fimction is sfiply the imaginary part of the inverse dielectric function, Im(-1 / s(q, E)) [2,3] [3]. For molecular liquids, optical absorption spectra below -7 eV [4] and Compton profiles [5] [6][7][8][9]. In particular, we have measured the equivalent of an absorption spectrum for liquid water with IXS [6,7] [8,9].…”

X-Ray Scattering and Fluorescence From Atoms and Molecules

“…35 The absolute scale was then determined using the Bethe sum rule. 29 The variation of the value of the momentum transfer over the spectra was ignored in the analysis.…”