Intracrystalline self-diffusion of methane adsorbed in NaA zeolite was deduced from proton spin-spin relaxation measurements. It was found that, for filling factors of up to 3 molecules per cage, the data were described by:

D(cm2/s) = 1.6 x 10-7 exp[-2500/T]

J.M.Allonneau, F.Volino: Zeolites, 1986, 6[6], 431-3