Experimental observation of ballistic atom exchange on metal surfaces

A ballistic (nonthermal) exchange process between vapor-deposited atoms and surface atoms is observed by field ion microscopy. A small fraction (11%) of lr atoms impinging on a Rh(100) surface held at 77 K embed themselves into the surface layer during condensation. Observation of exchange at temperatures well below those required for thermal exchange (330 K) indicates that it is possible for an atom to transfer some of its energy of condensation into motion along the surface. The fact that only 11% of the atoms undergo exchange implies that the transfer is inefficient.