The kinetics of absorption of H and D into 3N5-purity wire were investigated at temperatures of 78 to 230K. At pressures greater than about 0.1Pa, the rate of absorption was controlled by diffusion into the metal and the amount of H or D which was absorbed was proportional to the square root of elapsed time. It was suggested that diffusion occurred mainly in the β phase, which formed just beneath the surface of the filament. Very large isotope effects were observed at low temperatures; the ratio of the diffusion coefficients for H and D being equal to approximately 220 at 78K. This ratio decreased as the temperature was increased and, above 160K, it was constant at a value of 3.5. The Arrhenius plots for H and D diffusion both exhibited sudden changes in slope (table 161).

J.M.Guil, D.O.Hayward, N.Taylor: Proceedings of the Royal Society A, 1973, 335[1601], 141-61

Table 161

Parameters for H and D Diffusion in Ta