The dynamics of the CH3CN molecule in the isotropic phase and in a nematic solution

NMR lineshape studies of acelonitrile in the isotropic and the liquid-crystalline nematic phase of PCH have been performed. The scalar relaxation of the second kind due to the presence of the 14 N quadrupolar nucleus has been confirmed as the most important relaxation mechanism for this molecule in both the isotropic and the anisotropic phase. It has been found largely responsible for the selective broadening on 13 C and 1 H transitions. A minor contribution arising from intramolecular dipolar relaxation mechanism has also been investigated. Linewidth analysis of the NMR spectra allowed us to determine the quadrupolar relaxation time T IN of the 14 N nucleus. This is connected to the correlation time for rotational diffusion perpendicular to the molecular symmetry axis. A possible explanation of a residual selective broadeining which effects the 13 C and 1 H NMR transitions and is not taken into account by this mechanism, is also given.