How Vibrationally Assisted Tunneling with STM Affects the Motions and Reactions of Single Adsorbates

A mechanism of vibrationally assisted tunneling is proposed, which combines the atomic tunneling from the vibrational states with the vibrational ladder climbing, to explain the recent experiments on adsorbate motions induced by inelastic tunneling currents with a scanning tunneling microscope. Particularly, the hydrogen-bond exchange reaction within a single-water-heavy-water dimer on a Cu(110) surface, and Co adatom hopping on a Cu (111) surface, are analyzed. It is found that the vibrationally assisted tunneling mechanism can play a key role in the adsorbate dynamical motion when the energy of the relevant vibrational excitation is lower than the barrier for motion or reaction.