Elementary processes of vibrationally mediated motions of single adsorbed molecules

Elementary processes of motions of single adsorbed molecules on metal surfaces induced by inelastic tunneling currents with scanning tunneling microscope are discussed in conjunction with novel experimental results. A coherent multiple-step vibrational ladder climbing following a direct excitation of the reaction coordinate (RC) mode, or an indirect excitation of the RC mode through the anharmonic coupling to the high-frequency mode excited by tunneling electrons, to overcome the potential barrier along the RC associated with the relevant motions are combined to gain a deep insight into how competing different reaction pathways can be selectively activated within a single adsorbed molecule.