Abstract
The hopping motion of methylthiolate, CH3S, on Cu(111) was effectively induced by injecting tunneling electrons from the tip of a scanning tunneling microscope (STM). When the tunneling electrons are injected into an isolated CH3S at liquid He temperature in which the motion is originally frozen, the hopping phenomenon of CH3S from a hollow site to a neighboring hollow site is observed. This phenomenon shows a clear threshold in the applied bias voltage corresponding to the vibrational excitation energy of the C–S stretching mode in CH3S. We suggest a model in which the hindered translational mode, directly related to the hopping motion, is excited in accordance with the excitation of the C–S stretching mode through anharmonic coupling.