STUDY OF MOLECULAR MOTIONS IN 2-ADAMANTANONE BY NUCLEAR-MAGNETIC-RESONANCE

The temperature dependence of proton and carbon spin-lattice relaxatio n rates in 2-adamantanone is measured. The present experiments are ana lyzed in terms of relaxation resulting from intramolecular reorientati on modulation of the spin-spin interaction. In the plastic phase the m olecular reorientations involve a superposition of uniaxial rotation a nd tumbling reorientation of the dipolar axis. The calculation of the corresponding autocorrelation function is made by using a Frenkel mode l. The resulting expression for T-1 leads to a determination of the pl astic phase residence times in good agreement with values previously d educed from quasi-elastic neutron scattering and dielectric relaxation . In the low-temperature phase the motions are completely frozen and T -1 is rather constant.