Abstract
For different models of molecular motions, correlation times of cubic reorientations are calculated from the intramolecular 1H spin lattice relaxation time determined by studying powdered solid solutions of C10H16 and C10D16 at room temperature. The effect of isotropic librations on intramolecular spin-lattice relaxation and second moment has been calculated for single crystal and powder samples. The best agreement with the correlation time values calculated from powder neutron scattering experiments is obtained for a model where the molecules reorient by 90° jumps about the crystallographic C4 axes: τc4 -1=(5·3 ± 0·5)1012 exp [-(1395 ± 20)/T[°K]] s-1. This conclusion is in agreement with a detailed analysis of incoherent neutron scattering on single crystal of adamantane (preceding paper).