Magnetic Relaxation Spectroscopy with Ionic Solutions

Abstract

When the protons in a liquid are subjected to varying magnetic interactions, and a rapid averaging is prevented, it is possible to distinguish liquid elements, chemically similar, but differing in the amount of relaxation ∫₀^tdt′/T. The customary ac modulation of the magnetic field produces the required transient conditions. The phenomena of line broadening, line shift, and reversal of magnetization with time help to recognize the phases. The signal of the weak relaxation phase can easily be diminished by inducing eddy currents in the magnet iron. Additional non‐uniformities can be made in water by introducing dia‐ or para‐magnetic ions. An analysis of the processes of relaxation and adsorption shows that these water molecules or protons prevail in the observation for which the time of adsorption is close to the local relaxation time. The transient rate of relaxation of the entire sample is approximately equal to this rate of adsorption, and to the sweep frequency at which the magnetizations of the phases balance. The life time found for the protons in the inner layer of water surrounding trivalent ions, by studying concentrated diamagnetic solutions, is about 10 msec. For dilute paramagnetic solutions the values range from three hundred to one micro second, decreasing with the distance to the ion, increasing its magnetic moment. The activation energy involved times the power of its dependence upon the distance to the center ion, is 20 kcal/mole. The effective size of the atmosphere changes from one or two layers for dilute to two or three layers for concentrated solutions. Ice crystals with four layers radius and five milliseconds life time show up.