Anisotropic molecular reorientations of adamantane in its plastic solid phase: ¹H N.M.R. relaxation study in solid solutions of C₁₀H₁₆ and C₁₀D₁₆

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).