ROTATIONAL AND TRANSLATIONAL MOTIONS OF N-NONADECANE IN THE UREA INCLUSION COMPOUND AS EVIDENCED BY INCOHERENT QUASI-ELASTIC NEUTRON-SCATTERING

Incoherent quasielastic neutron scattering (IQNS) experiments have been performed on semi-oriented samples of n-nonadecane/urea-d4. Using two experimental geometries, we were able to show that large amplitude translations of the hydrocarbon chains in the c direction as well as rotations about the main molecular axis are effective in the high temperature disordered phase of the compound. In this paper, we have elaborated a phenomenological model in order to analyze quantitatively and separately the translations and rotations of the n-nonadecane molecules included in the urea channels. Our IQNS results are discussed and compared to literature data.