Spin diffusion of dipolar energy in NQR

The theory of spin diffusion was extended to the case of nuclear dipolar or der in solids containing paramagnetic impurities and nuclei with spin I > 1 /2 having nuclear quadrupole moment. We show that spin diffusion process of dipolar order takes place in solids containing paramagnetic impurities. At the start of relaxation process, the direct relaxation regime is realized with non-exponential time dependence. Then the relaxation regime will be ch anged to diffusion-limited one. Using obtained expressions for the spin lat tice relaxation times for these two relaxation regimes, the diffusion coeff icient of the dipolar older in nuclear quadrupole resonance can be estimate d from experimental data. (C) 2000 Elsevier Science B.V. All rights reserve d.