The tunneling current from a scanning tunneling microscope was used to image and dissociate single O 2 molecules on the Pt(111) surface in the temperature range of 40 to 150 K. After dissociation, the two oxygen atoms are found one to three lattice constants apart. The dissociation rate as a function of current was found to vary as I 0.860.2 , I 1.860.2 , and I 2.960.3 for sample biases of 0.4, 0.3, and 0.2 V, respectively. These rates are explained using a general model for dissociation induced by intramolecular vibrational excitations via resonant inelastic electron tunneling. [S0031-9007(97)

We present a density functional theory study of water adsorption on metal surfaces. Prototype water structures including monomers, clusters, one-dimensional chains, and overlayers have been investigated in detail on a model system-a Pt͑111͒ surface. The structure, energetics, and vibrational spectra are all obtained and compared with available experimental data. This study is further extended to other metal surfaces including Ru͑0001͒, Rh͑111͒, Pd͑111͒, and Au͑111͒, where adsorption of monomers and bilayers has been investigated. From these studies, a general picture has emerged regarding the water-surface interaction, the interwater hydrogen bonding, and the wetting order of the metal surfaces. The water-surface interaction is dominated by the lone pair-d band coupling through the surface states. It is rather localized in the contacting layer. A simultaneous enhancement of hydrogen bonding is generally observed in many adsorbed structures. Some special issues such as the partial dissociation of water on Ru͑0001͒ and in the RT39 bilayer phase, the H-up and H-down conversion, and the quantum-mechanical motions of H atoms are also discussed.

The existence and nature of end and central plasmon resonances in a linear atomic chain, the 1D analog to surface and bulk plasmons in 2D metals, has been predicted by ab initio time-dependent density functional theory. Length dependence of the absorption spectra shows the emergence and development of collectivity of these resonances. It converges to a single resonance in the longitudinal mode, and two transverse resonances, which are localized at the ends and center of the atom chains. These collective modes bridge the gaps, in concept and scale, between the collective excitation of atomic physics and nanoplasmonics. It also outlines a route to atomic-scale engineering of collective excitations.

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