Single molecule vibrational spectroscopy of N2 on Cu(1 1 0)

Vibrational spectra of single N2 molecules on Cu(1 1 0) have been measured using inelastic electron tunnelling spectroscopy with a scanning tunnelling microscope (STM-IETS). At 5 K, N2 exhibits a molecular stretch vibrational loss at 265 meV. Two adsorbate–substrate modes are also observed, at 11 and 36 meV, which are assigned to a frustrated translation and to a mode involving the molecule vibrating against the substrate, respectively. These results point to chemisorbed N2, with the molecular axis aligned perpendicular to the substrate. On the basis of earlier studies in the monolayer regime, it is likely that the isolated molecules studied here are associated with Cu vacancy sites.