High transient mobility of chlorine on TiO2(110):: Evidence for "cannon-ball" trajectories of hot adsorbates

Scanning tunneling microscopy was used to study the initial stages of Cl-2 adsorption on TiO2(110). Cl atoms adsorb on the rows of fivefold coordinated surface Ti atoms, and mostly form well separated pairs (average distance 26 Angstrom, atoms can be two or three rows apart). Abstractive adsorption results in 10% single Cl adatoms. We propose that Cl-2 dissociates in an approximately upright position. The outer Cl atom is emitted along the bond axis and can surmount the substrate bridging oxygen rows in a "cannon-ball"-like trajectory. Channeling along the Ti rows leads to large average Cl-Cl distances.