Study of molecular rotations in some aromatic compounds by cold-neutron scattering

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Abstract
The rotational motion of benzene, toluene, and phenol molecules in the liquid state has been studied by incoherent inelastic neutron scattering. The experiments have been carried out at DIN‐1 spectrometer in Dubna. The observed area and broadening of the quasielastic peaks as a function of momentum transfer have been compared with those predicted by Larsson models. The area of the quasielastic peak as a function of κ2 shows a slightly oscillatory behavior. For the linewidth curves this behavior is smeared out by the term containing the classical diffusion constant that is larger than the term containing the Bessel functions. The transient nature of the liquids is discussed. The main parameters describing the molecular rotations obtained from the best fits are reported. By using the extrapolation technique, the generalized frequency distributions are obtained. These spectra show distinct peaks especially in the region 15–250 cm−1. All the corresponding transitions are in good agreement with the optical spectroscopic measurements.