Measurements were made of nuclear magnetic resonance relaxation times in pure or Cd-doped single crystals at temperatures ranging from 385 to 900K. The process which was responsible for relaxation was Na self-diffusion. The cation migration enthalpy was found to be 0.45eV, while the activation energy for intrinsic diffusion was 1.6eV.

Self-Diffusion Studies in Sodium Iodide Single Crystals by NMR Relaxation. I.M.Hoodless, J.H.Strange, L.E.Wylde: Journal of Physics - C, 1971, 4[17], 2742-8