Ballistic motion and abstraction in dimer dissociation at surfaces: Cl-2 on K

Non-traditional dissociation dynamics at surfaces, with charge transfer and diabatic motion, is studied for the model system of Cl-2 molecules impinging on the metal K. Three-dimensional molecular dynamics on simple but physically reasonable potential-energy surfaces is used to investigate the final fates of the dissociation fragments (Cl, Cl-) of the molecular ion, Cl-2(-), that is formed by electron transfer (harpooning) to Cl-2 from the K surface. The model study demonstrates that both abstraction (emission of neutrals) and ballistic motion can result from dissociative chemisorption. Our qualitative reasoning has strong implications on other chemisorption systems, like O-2 on alkali and other metals and halogens on Si, e.g., a proposed explanation for ballistically moving O atoms on Al