β-NMR and nuclear spin diffusion in a spatially disordered subsystem

The results of theoretical and experimental investigations of delocalization of nuclear polarization in spatially disordered media are presented. The experiment is based on the measurement of a depolarization of β-active 8 Li impurity nuclei (β-nuclei) in the spatially disordered subsystem of 8 Li- 6 Li nuclei in LiF single crystals. The process is determined by the dipole-dipole interaction in this subsystem and by its dipole interactions with nuclei of the 7 Li 19 F matrix. It is effective in a wide range of external magnetic fields H 0 = 200–3000 G owing to proximity of g -factors. The kinetics of a depolarization of β-nuclei at the 6 Li concentration c = 0.15–10.06% in fields H 0 = 200 and 1210 G is investigated. A satisfactory explanation of the results is based on the numerical-analytical simulation of the process.