Electron stimulated desorption of NO from step sites on Pt(112): The role of chemisorption site geometry on the cross section

Abstract

The electronic excitation of adsorbed NO on Pt(112) has been observed to cause mainly desorption. Species‐specific total desorption cross sections of terminally bound and bridged‐bound NO present exclusively on the step sites of Pt(112) have been measured using Fourier transform infrared reflection absorption spectroscopy (FT‐IRAS) as a sensitive detector of the surface coverage of various chemisorbed NO species. Other electron stimulated processes which might influence the measurement of these cross sections, such as electron stimulated fragmentation, site‐exchange, and occupied site density effects have been found to be unimportant. It was found for 275 eV electrons that terminally bound NO desorbs with a larger cross section (2.3×10⁻¹⁸ cm²) than bridged‐bound NO, which has a desorption cross section of 8.7×10⁻¹⁹ cm². This is the expected relationship between the total desorption cross sections for these two species, with the smaller cross section being observed for the bridged NO.