Adsorption and accommodation of Xe on Pt{111}

Studying transient mobility and energy loss using scanning tunneling microscopy

“…We note that assumptions 1-4 were essentially met in our earlier STM measurements of Xe on Ptl 111) [9]. The extent to which assumption 5 is correct would need to be tested experimentally by varying incident atom kinetic energies.…”

“…The adatom continues to travel along the terrace until it loses all of its initial energy either due to interactions with the surface atoms or because it hits the step edge, which acts as a perfect sink for atoms and energy. We do these calculations in the dilute limit in which there are no adatom-adatom interactions, a situation easily and routinely obtainable in STM experiments [9].…”

“…At low coverage essentially all Xe atoms are found by scanning tunneling microscopy (STM) to be at step edges, with only a very small fraction on terraces [9]. The incident atoms had a well defined direction in the laboratory frame, impacting 600 from normal incidence, and at random sites on the Pt{ 111 ) terraces.…”

“…It is motion to and reaction at these sites which are thought to determine many surface reaction rates [ 1,2]. While many measurements have been made of surface diffusion [5][6][7][8], the motion due to adsorbate momentum parallel to the surface upon adsorption or due to exothermic surface processes has received much less attention [9][10][11][12][13][14]. Only a handful of measurements have been made, and the results of these are in apparent…”

“…In one of the few experimental measurements made, for adsorption of Xe on Pt{ 111) at 4K, we have depended upon terrace widths to set a lower limit of several hundred Angstroms for the transient mobility [9]. At low coverage essentially all Xe atoms are found by scanning tunneling microscopy (STM) to be at step edges, with only a very small fraction on terraces [9].…”