Laser-induced diffusion of oxygen on a stepped Pt(1Â 1Â 1) surface

Laser-induced diffusion of atomic oxygen on a stepped Pt(1 1 1) surface has been studied using ultrashort pulses of near-infrared light for the generation of a hot electron distribution at the surface. The dissociative adsorption of molecular oxygen at steps on the Pt(1 1 1) surface has been used to generate a nonequilibrium distribution of an adsorbate by decorating the step edges selectively with chemisorbed atomic oxygen. The coverage at the step edges during adsorption and induced diffusion has been monitored by exploiting the sensitivity of optical second-harmonic generation (SHG) on surface symmetry, which is macroscopically broken by regular steps. The diffusion rate shows a strong nonlinear dependence on the absorbed laser fluence indicating that the diffusion process can be understood in the same framework as the well studied phenomena of desorption induced by multiple electronic transitions (DIMET). Description within an electronic friction model reveals a temperature-dependent friction coefficient which we attribute to an indirect excitation mechanism of the frustrated translations.