Diffraction of optical second-harmonic generation from a monolayer grating created by laser desorption of adsorbates can be used to study surface diffusion of molecules on substrates. Application of this novel technique to CO on Ni(111) yields a diffusion activation energy of 6.9 kcal/mol and a preexponential factor of ≃1.2 × ${10}^{-5\mathrm{}}$ ${\mathrm{cm}}^2$ ${\mathrm{s}}^{-1\mathrm{}}$.

• Received 8 August 1988

DOI:https://doi.org/10.1103/PhysRevLett.61.2883