MONOMER-DIMER SURFACE-REACTION MODEL - INFLUENCE OF THE DIMER ADSORPTION MECHANISM

We consider the monomer-dimer surface reaction without surface diffusion for various dimer adsorption mechanisms, described below. After a dimer impinges ''end on'' at an empty site, its bottom atom remains there while its top atom searches N greater than or equal to 1 sites, either in a local neighborhood (N-local models), or randomly located on the surface (N-random models), to find a second empty site. If one is found, the dimer can then adsorb dissociatively. The N-local models have a reactive window of finite width in the relative impingement rates, bordered by poisoning transitions, whereas the N-random models exhibit true bistability. As N increases, the reactivity is either strictly or effectively confirmed to relative impingement rates close to the stoichiometric ratio. We precisely analyze the limiting behavior as N --> infinity.