Experimental determination of the electron density of liquid H2O and D2O

X-diffraction experiments on liquids are most commonly analysed within the independent atom approximation (IAA), despite the fact that compounds of light elements may show deviations from this simple approximation. An analysis of high energy x-ray diffraction data on liquid water in terms of the electron density auto-correlation function is given. The analysis shows that some but not all deviations from the IAA can be accounted for by a charged atom model. This corroborates findings from Compton scattering experiments on solid water that the nature of hydrogen bonding is at least partly covalent. The electron densities in H2O and D2O are found to be indistinguishable within the limits of the present experiments. This is in agreement with the interpretation of the differences in the intermolecular structure of H2O and D2O as being quantum mechanical in origin, and not the effect of a differing interaction potential.