Adsorbed states and scanning tunneling microscopy induced migration of acetylene on Cu(110)

Lateral Hopping of CO on Ag(110) by Multiple Overtone Excitation

A novel type of action spectrum representing multiple overtone excitations of the v(M-C) mode was observed for lateral hopping of a CO molecule on Ag(110) induced by inelastically tunneled electrons from the tip of a scanning tunneling microscope. The yield of CO hopping shows sharp increases at 261±4  mV, corresponding to the C-O internal stretching mode, and at 61±2, 90±2, and 148±7  mV, even in the absence of corresponding fundamental vibrational modes. The mechanism of lateral CO hopping on Ag(110) was explained by the multistep excitation of overtone modes of v(M-C) based on the numerical fitting of the action spectra, the nonlinear dependence of the hopping rate on the tunneling current, and the hopping barrier obtained from thermal diffusion experiments.

Cotunneling model for current-induced events in molecular wires

Many phenomena in molecular transport junctions involve transitions between electronic states of the molecular wire, and, therefore, cannot be described adequately using the Landauer picture. We present a model for cotunneling processes in molecular wires. These are coherent second-order processes that can be observed at low temperatures. As an example, we consider the STM-induced dissociation of acetylene. The large voltage threshold for dissociation observed experimentally is naturally accounted for within the cotunneling model.