On the diffusion of `hotʹ adsorbates: a non-monotonic distribution of single particle diffusion lengths for CO/Cu(111)

The diffusion of highly excited (`hotʹ) CO molecules on Cu(111) produced by electron attachment in the course of vertical manipulation within a scanning tunneling microscope apparatus is studied at low temperatures. The majority of the excited molecules exhibit a diffusion length of one adsite only, whereas of the remaining molecules were found more often at the third rather than the second nearest neighbor. This indicates that ballistic (unscattered) movement plays an import role in the diffusion process. A Monte Carlo simulation estimates the probability of ballistic movement to be at least 15% per transgressed adsite.