VELOCITY DISTRIBUTIONS OF RECOMBINATIVELY DESORBED O-2 ORIGINATING FROM SURFACE AND SUBSURFACE OXYGEN RH(111)

Oxygen can exist either on the surface or in the sub-surface region of Rh(lll). There are clearly different thermal desorption signatures fo r these two states. In this Letter, we report on experiments examining the dynamical paths for oxygen recombination and desorption arising f rom the two states by measuring the velocity distributions of the deso rbing O-2. The results are well represented by identical Maxwell-Boltz mann velocity distributions, significantly hotter than the surface tem perature. Sire conclude that surface and sub-surface oxygen share a co mmon dynamical state prior to desorption.