Longitudinal deuteron relaxation time

Fig. 28.1. (a) Longitudinal and transverse Tj relaxation times for water as a function of filling ratio (with permission), (b) Longitudinal relaxation rate of deuterons as a function of pore radius for nitrobenzene-d, at 300 K . 

Vanderveen et al. studied D2O in Nafion membranes using MQ-filtered deuteron experiments as a function of the hydration level. They evaluated the T2 relaxation times and interpreted the results in terms of a hydration model with two water domains. Ohkubo and co-workers studied Nafion, as well as sulfonated poly(ethersulfone) membranes. They used diffusion-weighted H inversion-recovery measurements followed by Laplace-trans-form analysis of the distribution of longitudinal relaxation times and were able to distinguish water molecules in larger and smaller channels. 

Deuterium nuclei in water molecules have negligible asymmetry parameters and residual anisotropies. After correcting for the paramagnetic impurities present, that affect relaxation rates somewhat (35), one obtains from the experimental data a value of the longitudinal relaxation rate for the water deuterons in the bound state of 650 s 1. This value incorporates the quadrupolar coupling constant (above determined) and the correlation time for bound waters. Using the standard expression for quadrupolar relaxation (29,35) yields a value for t 1.6 ns. 

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