Anisotropic surface diffusion of CO on Ni(110)

Anisotropic surface diffusion of CO on Ni(110) has been studied using the newly developed technique of optical second-harmonic diffraction from a laser-induced CO monolayer grating. Two distinct orthogonal diffusion channels, along [11{}0] and [001], were found. The measured diffusion coefficients yield the diffusion activation energies Ed(11{}0)=1.1±{}0.2 kcal/mol and Ed(001)=3.1±{}0.4 kcal/mol and the preexponential factors D₀(11{}0)=(3.8±{}2.0)×{}10^-9 cm²/sec and D₀(001)=(4.8±{}4.4)×{}10^-6 cm²/sec. The anisotropy in the surface diffusion appears to cross over at T{~}160 K.