The migration of H upon the (100) surface was studied by linearly diffracting a laser-beam probe from a monolayer grating of adsorbed H. It was found that, at temperatures of between 110 and 161K, the Arrhenius plot revealed a marked levelling-off of the diffusion coefficient at about 144K (figure 20). This deviation was attributed to the appearance of quantum diffusion. It was suggested that the underlying surface diffusion was governed by an activation energy of 3.5kcal/mol.

X.D.Zhu, A.Lee, A.Wong, U.Linke: Physical Review Letters, 1992, 68[12], 1862-5

Figure 20

Diffusivity of H on the (100) Surface of Ni