Nuclear Dynamic Polarization and Spain‐Lattice Relaxation in Plastic Cyclohexane Doped with a Nitroxide Free Radical in Low Concentration
| Autor: | B. Meerovici, H. Verdun, F. Volino |
|---|---|
| Rok vydání: | 1972 |
| Předmět: |
Nitroxide mediated radical polymerization
Cyclohexane Doping Relaxation (NMR) Analytical chemistry General Physics and Astronomy Polarization (waves) Molecular physics law.invention chemistry.chemical_compound chemistry law Spin diffusion Critical radius Physical and Theoretical Chemistry Electron paramagnetic resonance |
| Zdroj: | The Journal of Chemical Physics. 57:2414-2421 |
| ISSN: | 1089-7690 0021-9606 |
| DOI: | 10.1063/1.1678604 |
| Popis: | In order to check the theory of spin diffusion with a new kind of sample, we present measurements of dynamic polarization and spin‐lattice relaxation, at 3300 G, on the plastic phase of cyclohexane doped with a nitroxide free radical. The EPR lines are sufficiently narrow to allow an ideal ``solid effect.'' The enhancement of the proton resonance was measured as a function of microwave power for various temperatures. The decay rate of these enhanced signals both as a function of temperature and radical concentration was studied, in order to determine the proton spin‐lattice relaxation time. The electronic spin‐lattice relaxation time was measured by the saturation method. The data were found to be fairly consistent with a rapid diffusion regime between −10 and −60°C. The critical radius (i.e., the radius of a sphere, centered on the electronic spin, inside which the diffusion coefficient is zero) was found to be ≃ 1.7 A. This value is much smaller than the distance between the free radical and the nearest... |
| Databáze: | OpenAIRE |
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