Laser-induced diffusion of atomic O on a stepped Pt(111) surface was studied by using ultra-short pulses of near-infrared light for the generation of a hot electron distributions at the surface. The dissociative adsorption of molecular O at steps on the Pt(111) surface was used to generate a non-equilibrium distribution of an adsorbate by decorating the step edges selectively with chemisorbed atomic O. The coverage at the step edges during adsorption and induced diffusion was monitored by exploiting the sensitivity of optical second-harmonic generation on surface symmetry, which was macroscopically broken by regular steps. The diffusion rate showed a strong non-linear dependence upon the absorbed laser fluence indicating that the diffusion process could be understood in the same framework as the well-studied phenomena of desorption induced by multiple electronic transitions. An electronic friction model revealed a temperature-dependent friction coefficient which was attributed to an indirect excitation mechanism of the frustrated translations.

Laser-Induced Diffusion of Oxygen on a Stepped Pt(111) Surface. K.Stépán, M.Dürr, J.Güdde, U.Höfer: Surface Science, 2005, 593[1-3], 54-66