Study of molecular motion in modification C of the n-alkane n-C33H68 by means of incoherent quasielastic neutron scattering

Abstract

By means of incoherent quasielastic neutron scattering experiments on uniaxially oriented n‐C₃₃H₆₈ samples it was possible to give an experimental proof that molecular motion in modification C is composed of rotational and translational components. The analysis of the quasielastic spectra was performed comparing them to theoretical scattering laws, which were calculated on the basis of different models, compatible with the results of former x‐ray, NMR and ir experiments. This procedure leads to the conclusion that translational jumps in the chain direction, the jump distance 1.27 Å, and rotational 180° jumps take place independently. At 67 °C the jump rates are: v_t = (2.6±0.4) ×10⁸ s⁻¹ and v_r= (5±2) ×10⁷ s⁻¹, respectively.