The diffusion of H at pressures down to 10-8torr was investigated by using mass spectroscopy. At pressures of 0.6 to 380torr, and 200 to 400C, the diffusivity was described by:

D (cm2/s) = 5.7 x 10-3 exp[-5.7(kcal/g-atom)/RT]

J.A.Balovnev: Zhurnal Fizika Khimii, 1974, 48[3], 719-20