Chemisorption and dissociation of single oxygen molecules on Ag(110)

The chemisorption of single oxygen molecules on Ag(110) and the dissociation of the adsorbed molecules induced by tunneling electrons were studied at 13 K using a variable-low-temperature scanning tunneling microscope. Two predominant types of chemisorbed O-2 molecules were identified, one with the O-2 molecular axis aligned along the [001] direction of the substrate [O-2(001)], and the other with the molecular axis aligned along the [1 (1) over bar0] direction [O-2(1 (1) over bar0)]. Tunneling of electrons between the scanning tunneling microscope tip and O-2(001) caused the molecule either to rotate or dissociate, depending on the direction of electron tunneling. In contrast, electron tunneling caused O-2(1 (1) over bar0) to dissociate regardless of tunneling direction. In addition to O-2(001) and O-2(1 (1) over bar0), several other oxygen species and their dynamical behaviors were observed. (c) 2005 American Institute of Physics.