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 for these two states. In this Letter, we report on experiments examining the dynamical paths for oxygen recombination and desorption arising from the two states by measuring the velocity distributions of the desorbing O-2. The results are well represented by identical Maxwell-Boltzmann velocity distributions, significantly hotter than the surface temperature. Sire conclude that surface and sub-surface oxygen share a common dynamical state prior to desorption.