Vibrational mode specific bond dissociation in a single molecule.

Tunneling electrons from a scanning tunneling microscope were used to image and dissociate single O(2)-water-O complexes adsorbed on a Ag(110) surface at 13 K. The dissociation rate was measured as a function of the energy and current of the tunneling electrons; an increase was found in this rate by a factor of approximately 100 at an electron energy equivalent to that of the O-H (D) stretch vibration. These results indicate that the rate of bond dissociation is competitive with the other energy dissipation pathways of the stretch vibration. The barrier to the dissociation of the water molecules is lowered by the formation of hydrogen bonds with oxygen species.