The surface diffusion of D and H on (001) planes at low coverages was studied by using laser-induced thermal desorption techniques. The surface diffusion coefficients could be described by the expressions:

D:     D (cm2/s) = 0.00046 exp[-4.1(kcal/mol)/RT]

H:     D (cm2/s) = 0.00069 exp[-3.6(kcal/mol)/RT)

at temperatures ranging from 260 to 300K. The observed isotope effect was somewhat larger than that predicted by simple transition-state theory, but was within the limits of experimental error. It was concluded that quantum-mechanical tunnelling played only a minor role in the surface migration of H on Ru at these temperatures.

G.H.Mak, J.L.Brand, B.G.Koehler, S.M.George: Surface Science, 1987, 188[1-2], 312-20

Table 250

Diffusion of CO on Ru(001) and Ru(S)[15(001) x 2(100)] Surfaces