Excess amounts of D and H were dissolved by using the liquid-H quenching technique. The diffusion of the isotopes was then monitored, by using resistivity methods, at temperatures of between 220 and 350K. An anomalous mass effect was detected, and the activation energies for diffusion were estimated to be 34.3kJ/mol for H and 36.1kJ/mol for D. The smaller value for H diffusion was not expected on the basis of classical diffusion theory. The value of the ratio increased with decreasing temperature, and was greater than the classical value of 1.414 at the lowest temperatures used.

Isotope Effect in Hydrogen Diffusion in Copper. K.Yamakawa, K.Nunogaki, F.E.Fujita: Journal of the Physical Society of Japan, 1986, 55[3], 877-84