Vibration of H atomic chains on Ni(1Â 1Â 0) measured by scanning tunneling microscope (STM) light emission spectroscopy

We have measured the scanning tunneling microscope (STM) light emission spectrum of hydrogen atoms (H) adsorbed on a Ni(1 1 0) surface. The spectrum contains periodic fine structures, whose period corresponds to the vertical vibrational energy of the adsorbed H atom. This energy showed the expected isotope shift when H was replaced by deuterium (D). Hence it is concluded that the periodic structures are caused by the vibrational motion of H.