Proton NMR Relaxation in Hydrous Melts

J. Braunstein, A. L. Bacarella, B. M. Benjamin, L. L. Brown, C. Girard
1976 ECS Proceedings Volumes  
Pulse and continuous wave NMR measurements are reported for protons in hydrous melts of calcium nitrate at tempera tures between -k° and 120°C. Although measured in different temperature ranges, spin-lattice (Tp) and spin-spin (T2 ) re laxation times appear to be nearly equal to each other and proportional to the self-diffusion coefficients of solute metal cations such as Cd2+. At temperatures near 50°C mean Arrhenius coefficients, A Hp, (kcal/mol), are 7 .9 , 7 .3 , and U.8, respectively, for
more » ... elts containing 2.8, ¿+.0 and 8.0 moles of water per mole of calcium nitrate, compared to k .6 kcal/mol for pure water. Temperature dependence of Tp and T2 in Ca(NC>3)2"2.8 H2O between -k and 120°C are non-Arrhenius and can be represented by a Fulcher-type equation with a "zero mobility temperature" (T0) of 225 K, close to the value of To for solute diffusion, electrical conductance and vis cosity. Resolution of the relaxation rates into correlation times for intramolecular (rotational) and intermolecular (translational) diffusional motion is discussed in terms of the Bloembergen-Purcell-Pound and more recent models for dipolar relaxation.
doi:10.1149/197606.0544pv fatcat:dmwlxbcwtzdyxeaf2zgfxj26dq