DIRECT SUBSURFACE ABSORPTION OF HYDROGEN ON PD(III)

We summarize and discuss some of the available experimental and theore tical data important for understanding the role played by subsurface s ites in dissociative chemisorption calculations for the H-2/Pd(111) sy stem. Then we use a semi-empirical potential energy surface (PES) to m odel the interaction of a H-2 molecule impinging on a Pd(111) surface. The London-Eyring-Polanyi-Sato (LEPS) construction has been extended to make direct subsurface absorption possible. A two-dimensional wave packet calculation is used to find qualitative trends in the direct su bsurface absorption and to reveal the time scales involved. We suggest that a partial in-plane relaxation occurs for the slowest incoming pa rticles, thus resulting in a higher direct subsurface absorption proba bility for low energies. (C) 1996 American Institute of Physics.