Proton NMR Relaxation in Hydrous Melts *

Autor:	L. L. Brown, C. Girard, B. M. Benjamin, J. Braunstein, A. L. Bacarella
Rok vydání:	1976
Předmět:	Arrhenius equation Spin–spin relaxation symbols.namesake Chemistry Intermolecular force Inorganic chemistry Spin–lattice relaxation symbols Proton NMR Solvation Analytical chemistry Relaxation (physics) Resonance
Zdroj:	ECS Proceedings Volumes. :544-559
ISSN:	2576-1579 0161-6374
DOI:	10.1149/197606.0544pv
Popis:	Pulse and continuous wave NMR measurements are reported for protons in hydrous melts of calcium nitrate at temperatures between -4 and 120/sup 0/C. Although measured in different temperature ranges, spin-lattice (T/sub 1/) and spin-spin (T/sub 2/) relaxation times appear to be nearly equal to each other and proportional to the self-diffusion coefficients of solute metal cations such as Cd/sup 2 +/. At temperatures near 50/sup 0/C, mean Arrhenius coefficients ..delta.. H/sub T/sub 1// (kcal/mol) are 7.9, 7.3, and 4.8, respectively, for melts containing 2.8, 4.0, and 8.0 moles of water per mole of calcium nitrate, compared to 4.6 kcal/mol for pure water. Temperature dependence of T/sub 1/ and T/sub 2/ in Ca(NO/sub 3/)/sub 2/-2.8 H/sub 2/O between -4 and 120/sup 0/C are non-Arrhenius and can be represented by a Fulcher-type equation with a ''zero mobility temperature'' (T/sub 0/) of 225/sup 0/K, close to the value of T/sub 0/ for solute diffusion, electrical conductance and viscosity. 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. (auth)
Databáze:	OpenAIRE
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