X-RAY-SCATTERING BY WATER-MOLECULES STUDIED BY USING SYNCHROTRON-RADIATION

The energy spectra of free water molecules were measured at scattering angles 2 theta ranging from 10.5 degrees to 75.7 degrees, using an an gle-dispersive-type diffractometer and synchrotron radiation as an X-r ay source. A silicon (111) monochrometer was used to obtain incident X -rays with the wavelengths of (1.543/n) Angstrom (n = 1, 3, 4, 5). Obs erved inelastic scattering peaks are clearly separated from elastic on es at s values [s = (4 pi/lambda) sin theta] larger than 8 Angstrom(-1 ). The increase of the separation with an increasing s value was consi stent with the classical theory of the Compton shift. The total (elast ic plus inelastic) intensities were obtained over a range of s = 0.74- 5.0 Angstrom(-1). Experimental difference intensities Delta sigma(ee) and Delta sigma(ne) were obtained separately by combining the X-ray an d high-energy electron scattering data. The experimental results are i n reasonable agreement with the theoretical intensities calculated fro m SCF and CI molecular wave functions with a basis set of double-zeta plus polarization functions. (C) 1994 John Wiley and Sons, Inc.