Non-exponential magnetic relaxation of I=3/2 nuclear spins in solids

Abstract

A nuclear magnetic double-resonance experiment, performed on the 23Na spin system in a single crystal of NaNO2 at 130 K, has shown that the spin-lattice relaxation is magnetic, as opposed to quadrupolar, at that temperature. The approach to equilibrium of the high-frequency satellite of this spin system, after excitation by a selective 90 degrees pulse, was found to be quite non-exponential at 130 K and roughly in agreement with a simple theory. The approaches to equilibrium of both the high-frequency satellite and the central resonance after excitation of the latter by a selective 90 degrees pulse were found to be exponential, in marked contrast to the theory. The reason for the discrepancy is not known.