ON THE DIFFUSION OF HOT ADSORBATES - A NONMONOTONIC DISTRIBUTION OF SINGLE-PARTICLE DIFFUSION LENGTHS FOR CO CU(111)/

The diffusion of highly excited ('hot') CO molecules on Cu(111) produc ed by electron attachment in the course of vertical manipulation withi n a scanning tunneling microscope apparatus is studied at low temperat ures. The majority of the excited molecules exhibit a diffusion length of one adsite only, whereas of the remaining molecules were found mor e often at the third rather than the second nearest neighbor. This ind icates that ballistic (unscattered) movement plays an import role in t he diffusion process. A Monte Carlo simulation estimates the probabili ty of ballistic movement to be at least 15% per transgressed adsite. ( C) 1998 Elsevier Science B.V. All rights reserved.