Direct Observation of Scattering Angle Dependence of the Inelasticity Effect on the Interference Term Obtained from Time-of-Flight Neutron Diffraction Experiments

Scattering angle dependence has been experimentally examined for inelasticity effect on the intramolecular interference term observed from the time-of-flight neutron diffraction method. Internuclear distance and its root-mean-square displacement for liquid pure D2O, C6D6 and CCl4, have been determined from the least squares fitting analysis of the observed total interference term in the high-Q region. Although "apparent shrinkage" in the intramolecular distance has been observed obviously for the light nuclei pair at large scattering angle data (2 theta > ca. 70 degrees), it has been revealed that the apparent shrinkage in the D center dot center dot center dot D distance for D2O and C6D6, in which the inelasticity effect is expected to be most significant, is found to be suppressed well within ca. 1% for the data observed for the scattering angle below ca. 2 theta < ca. 50 degrees. Structural parameters determined have been compared with those determined from the gas-phase electron diffraction method in order to obtain insight of the effect of intermolecular interaction to molecular geometry in the liquid phase.