Bethe Surface of Liquid Water Determined by Inelastic X-Ray Scattering Spectroscopy and Electron Correlation Effects

Abstract

By means of inelastic X-ray scattering spectroscopy, the generalized oscillator strength (GOS) of liquid water has been experimentally determined over a range 0.69 ≤ q ≤ 3.59 a.u., where q is the momentum transfer. The Bethe surface was constructed from the GOS, and the loss function, the dielectric response function, and the static structure factor were deduced. It was found that the GOS of liquid water is dominated by individual molecular properties over the q range studied, and that the static structure factor agrees quite well with a calculation including electron-electron correlation effects.

The complete optical spectrum of liquid water measured by inelastic x-ray scattering

“…Owing to the lack of experimental data, such calculations have to rely on cross sections of liquid water estimated from the gas phase cross-section data with a number of assumptions or extrapolated from the optical data of Heller et al (6). The complete optical spectrum of liquid water reported in this work, together with the previously measured generalized oscillator strength distributions at higher momentum transfers (9), should improve the reliability of these calculations.…”

“…by IXS (9) and have substantiated experimentally that IXS of liquid water can provide the same spectra as optical spectroscopy as long as the momentum transferred is less than Ϸ0.3 a.u (10). Unfortunately, however, low signal-to-noise ratio problems prevented us from obtaining the quantitative optical oscillator strength distribution.…”

The Bethe surface of liquid water

“…The energy loss function qz (E, K) from the Sendai data is obtained as follows: All possible data sources from [2,3] are scanned and values for 772 (E, K) are extracted at various (E, K)-points. Because data are available only in limited (E, K)-ranges, gridding and interpolation and extrapolation methods, respectively, are used to produce data on a regular mesh over a wider range of E and K values (O~K < 3.6 au., 0< E <150 eV).…”

“…After the completion of the semi-empirical determination [1] of the dielectric-response function, we became aware of the recent measurements by the Sendai group [2,3].…”

X-Ray Scattering and Fluorescence From Atoms and Molecules

“…Complete studies of any Bethe surface using inelastic x-ray scattering are difficult due to the small cross section and the need to reliably remove the intense elastic scattering peak. Some studies have been done using x-ray scattering, 30 but most have used electron scattering on gaseous targets. 31 calculated from the GOS, e.g.…”