PROBING THE (DUAL) REPULSIVE WALL IN THE INTERACTION OF O-2, N-2, AND AR WITH THE AG(111) SURFACE

We have performed molecular beam scattering experiments of O-2, N-2, and Ar from the Ag(111) surface in the translational energy regime from 0.2 to 2.6 eV and at surface temperatures of 600 and 150 K. The experiments were carried out to probe the repulsive part in the particle-surface interaction potential. It is shown that the scattering dynamics of the systems N-2-Ag(111) and Ar-Ag(111) is characteristic of physisorption systems. The scattering data for the system O-2-Ag(111) shows that both the physisorption and chemisorption part of the interaction potential are probed in the experiment. For ''normal incidence energies'' exceeding a threshold energy, the barrier to the chemisorption part of the interaction potential can be crossed. An upper limit for this threshold is E(i) cos(2) theta(i) = 0.3 eV. Although the chemisorption region is probed, the (dissociative and nondissociative) chemisorption probability remains negligible. (C) 1995 American Institute of Physics.