Study of the adsorption structure of NO on Pt(111) by scanning tunneling microscopy and high-resolution electron energy-loss spectroscopy

The structure of nitric oxide (NO) on a Pt(111) surface was studied by scanning tunneling microscopy (STM) and high-resolution electron energy-loss spectroscopy (HREELS). The coexistence of two species is observed by STM after saturating the surface with NO at 70 K and annealing to 215 K. Two pairs of NO and PtN stretching vibrational frequencies are observed in HREELS spectra after annealing, which are assigned to the two species observed by STM. Comparison between the spectra of HREELS and infrared absorption spectroscopy (IRAS) indicates that IRAS is less sensitive to the lower-frequency mode. A new model for the adsorption structure of NO on the Pt(111) surface is proposed and discussed.