How oxygen adsorbs on TiO2(110)

The sequence shows how a O2 molecule first binds at an oxygen vacancy, then dissociates into two single oxygen adatoms. One of them eventually heals the vacancy. See: P. Scheiber, A. Riss, M. Schmid, P. Varga, U. Diebold, Observation and destruction of an elusive adsorbate with STM: O2/TiO2(110). Phys. Rev. Lett. 105 (2010) 216101