A neutron inelastic scattering study of the chloroethanes

Neutron inelastic scattering measurements are reported for six chloroethane samples. Absolute theoretical intensities have been calculated for vibrational inelastic events which are in good agreement with the experimental results. In some cases the calculated intensities show a dependence on the symmetry species of the normal modes concerned and this is also confirmed experimentally. The measured torsional frequencies for CH 3 CCl 3 and CH 3 CHCl 2 lead to new values of the barriers to internal rotation in these molecules. A discussion is given of the analysis of the low energy scattering with particular emphasis on the difficulties of obtaining unambiguous quantitative data concerning molecular motion in the liquid state. Simple self-diffusion coefficients are obtained for the chloroethanes studied.