The diffusion of H in crystalline material was measured at temperatures ranging from 50 to 220K. It was found that the temperature dependence of the diffusivity could be described by a power law of the form, D = constant x T5.6. The diffusivities ranged from 10-18, to 10-14cm2/s at about 200K. A transition to thermally activated diffusion then occurred. The low-temperature behavior was attributed to tunnelling.

C.Langpape, S.Fabian, C.Klatt, S.Kalbitzer: Applied Physics A, 1997, 64[2], 207-10