Abstract
In general the analysis of neutron isotopic substitution experiments in terms of
partial structure factors and partial pair distribution functions is based on the
assumption that the structure of isotopic variants of a molecule is identical. This
assumption is clearly only an approximation especially in the case of hydrogen
bonding molecular liquids like liquid water and structural isotope effects have been
measured with X-rays for more than 20 years. A analysis method of neutron isotope
data is presented that avoids the necessity to assume structural equality and allows
the determination of the isotope effect in the hydrogen-hydrogen partial structure
factor of liquid water from neutron data. It is shown that a combination of X-ray
and neutron scattering measurements allows in principle the determination of the
isotope effects on all all partials structure factors of liquid water.
