Nuclear Spin-Lattice Relaxation Via Paramagnetic Centers Without Spin Diffusion

Abstract

Experiments have been performed which study the relaxation of a nuclear spin system by paramagnetic impurities under conditions which inhibit spin diffusion. When spin diffusion is effectively absent, the magnetization is found ultimately to approach its equilibrium value as $\mathrm{exp}[\ensuremath{-}{(\frac{t}{{\ensuremath{\tau}}_{1}})}^{\frac{1}{2}}]$. An expression is obtained describing the relaxation of such a diffusionless spin system valid for all times and in agreement with experiment. Under suitable conditions higher order spin diffusion effects are also observed.