3.
The energy spectra of free water molecules were measured at scattering angles 2θ ranging from 10.5° to 75.7°, using an angle-dispersive-type diffractometer and synchrotron radiation as an X-ray source. A silicon (111) monochrometer was used to obtain incident X-rays with the wavelengths of (1.543/
n) Å (
n = 1,3,4,5). Observed inelastic scattering peaks are clearly separated from eleastic ones at
s values [
s = (4π/λ) sin Å] larger than 8 Å
?1. The increase of the separation with an increasing
s value was consistent with the classical theory of the Compton shift. The total (elastic plus inelastic) intensities were obtained over a range of
s = 0.74–5.0 Å
?1. Experimental difference intensities Δσ
ee and Δσ
ne were obtained separately by combining the X-ray and high-energy electron scattering data. The experimental results are in reasonable agreement with the theoretical intensities calculated from SCF and CI molecular wave functions with a basis set of double-zeta plus polarization functions. © 1994 John Wiley & Sons, Inc.
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