Influence of paramagnetic impurities on molecular self‐diffusion as seen by nuclear spin‐lattice relaxation and dynamic polarization

Measurements, near the melting point, of nuclear spin‐lattice relaxation and dynamic polarization in plastic cyclohexane doped with a nitroxyde free radical show deviations from the expected spin‐diffusion theory. These deviations are explained by the quenching of the molecular self‐diffusion around the radical and interpreted semiquantitatively in terms of a two zone model. It is shown that the quenching extends up to more than four intermolecular distances and the spin‐diffusion coefficient in this region is shown to be around 0.3× 10−12 cm2 sec−1. It seems that similar measurements would be of interest in any crystal which exhibits NMR motional narrowing due to fast molecular self‐diffusion.

[1]  H. Verdún,et al.  Nuclear Dynamic Polarization and Spain‐Lattice Relaxation in Plastic Cyclohexane Doped with a Nitroxide Free Radical in Low Concentration , 1972 .

[2]  J. E. Tanner.  Self‐Diffusion in Plastic Crystals , 1972 .

[3]  F. Volino,et al.  Etude des Mouvements Moléculaires dans li Cyclohexane Plastique à l'Aide d'une Sonde Radicalaire par Résonance Paramagnétique Electronique et Double Résonance Electronique Nucléaire , 1972 .

[4]  R. Baughman,et al.  Self-diffusion in crystalline hexamethylethane and cyclooctane* , 1972 .

[5]  P. A. Egelstaff.  Cooperative Rotation of Spherical Molecules , 1970 .

[6]  J. Sherwood,et al.  Lattice Defects in Plastic Organic Solids 4. A Comparison of Plastic Flow and Nuclear Magnetic Resonance Studies of Self-Diffusion in Camphene , 1970 .

[7]  S. Roeder,et al.  Molecular Motions in Several Solids Studied by Nuclear Magnetic Relaxation in the Rotating Frame , 1970 .

[8]  L. D. Graaf.  Study of molecular motions in cyclohexane and cyclopentane by cold-neutron scattering , 1969 .

[9]  G. Khutsishvili.  Reviews of Topical Problems: Spin Diffusion , 1966 .

[10]  J. Sherwood,et al.  Self Diffusion in Cyclohexane Single Crystals , 1966 .

[11]  M. Sugisaki,et al.  Self-Diffusion in Some Plastic Crystals , 1966 .

[12]  H. E. Rorschach.  Nuclear relaxation in solids by diffusion to paramagnetic impurities , 1964 .

[13]  L. Petrakis,et al.  Rotational Transition and Self‐Diffusion in Polycrystalline Succinonitrile , 1963 .

[14]  C. Jeffries.  Dynamic nuclear orientation , 1963 .

[15]  J. Korringa,et al.  THEORY OF SPIN PUMPING AND RELAXATION IN SYSTEMS WITH A LOW CONCENTRATION OF ELECTRON SPIN RESONANCE CENTERS , 1962 .

[16]  J. Korringa,et al.  Magnetic Spin Pumping in Fluids Contained in Porous Media , 1959 .

[17]  W. Brittin,et al.  Nuclear Magnetic Resonance Studies in Multiple Phase Systems: Lifetime of a Water Molecule in an Adsorbing Phase on Silica Gel , 1957 .

[18]  E. R. Andrew,et al.  A nuclear magnetic resonance investigation of solid cyclohexane , 1953, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences.