Measurement of the nuclear spin diffusion coefficient in organic glasses doped with paramagnetic centers: Orthoterphenyl and polymeric glasses |
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Authors: | B Meurer G Weill |
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Institution: | 1. Institut Charles Sadron, Centre National de la Recherche Scientifique and Université Louis Pasteur, 6 rue Boussingault, 67083, Strasbourg, France
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Abstract: | We have recently developed a method of studying spin diffusion coefficients by doping the materials with paramagnetic centers
and measuring the nuclear relaxation in a tilted rotating frame. Using this method, we measure here the spin diffusion coefficient
of orthoterphenyl, a molecular organic glass, and of three polymer glasses: poly(4-vinylpyridine), poly(vinylacetate) and
poly(methyl methacrylate). We explore a possible dependence of the measured orthoterphenyl spin diffusion coefficient on the
electronic relaxation time and concentration of the paramagnetic centers. We conclude that the experiments can be performed
at higher concentrations than previously thought. We also show that our method applies to polymers in the glassy state if
one works at sufficiently small tilt angle, in spite of a short value ofT
1ρ. We had anticipated that the distribution of proton pairs in these materials precludes the standard dependence of the spin
diffusion coefficient on the proton density and free induction decay characteristic decay time. Our results fully confirm
such expectation. |
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