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 scan ning tunneling microscopy (STM) and high-resolution electron energy-loss sp ectroscopy (HREELS). The coexistence of two species is observed by STM afte r 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 s pectra after annealing, which are assigned to the two species observed by S TM, Comparison between the spectra of HREELS and infrared absorption spectr oscopy (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, (C) 2000 Published by Elsevier Science B.V. All rights reserved.