The diffusion of T was studied by using time-lag techniques. The β-radiation which originated from T decay within a thin layer near to the external surface was used to monitor changes in T concentration with time in this layer. No passage of T atoms through the phase boundary was necessary, and no energy

barriers which might retard their passage could therefore interfere. The results for Pd, at temperatures of between 16.5 and 50C, could be described by:

D (cm2/s) = 1.05 x 10-2 exp[-6.35(kcal/mol)/RT]

G.Sicking, H.Buchold: Zeitschrift für Naturforschung A, 1971, 26[12], 1973-80