The diffraction of optical second-harmonic generation from a monolayer grating, created by the laser desorption of adsorbates, was used to study the surface diffusion of molecules on substrates. In the case of CO migration on (111) Ni surfaces, the data (table 15) could be described by:

D (cm2/s) = 1.2 x 10-5 exp[-6.9(kcal/mol)/RT]

X.D.Zhu, T.Rasing, Y.R.Shen: Physical Review Letters, 1988, 61[25], 2883-5

Table 15

Diffusivity of CO on the (111) Surface of Ni