Kinetics of the polarization transfer in spatially disordered spin systems: Depolarization of impurity beta-active nuclei

We performed theoretical and experimental studies of the delocalization of the nuclear polarization of impurity beta-active nuclei 8 Li in the spatially disordered system of 6 Li nuclei in LiF single crystals. The process is controlled by the dipole-dipole interaction of nuclear magnetic moments with other nuclei ( 7 Li, 19 F) in the crystal. It is effective in a wide range of magnetic fields H 0 = 150–3000 G as a result of a unique proximity of the g -factors of 8 Li and 6 Li nuclei: ( g ( 8 Li) − g ( 6 Li))/ g ( 6 Li) = 0.0057. The kinetics of the 8 Li depolarization is measured for an 6 Li concentration of 0.15%–10.06% and in the field H 0 of 200, 692 and 1210 G. A satisfactory explanation of the results is obtained on the basis of a numerical-analytical simulation of the process.