Adsorbed nitric oxide on iron(110)

Abstract

The adsorption of nitric oxide on an Fe(110) single crystal at temperatures 90–350 K has been investigated by HeI UPS and by Auger spectroscopy. Four adsorption states are detected in UPS depending on the substrate temperature. Molecular absorption states, α₁ at 90–110 K and α₂ at 110–170 K are observed. The α₂ state is preceded by some NO dissociation. A β adsorption state exists over a very wide temperature range of 170–290 K. It consists of NO chemisorbed amidst atomic N and O from the initial dissociation. Nitric oxide was found to initially dissociate at all substrate temperatures above 110 K. The extent of dissociation increased with temperature, being complete at above 300 K (d state). No measurable molecular NO was found to exist above 330 K. The lower temperature adsorption states are shown to undergo an irreversible conversion to the next highest temperature state upon heating the substrate: α₁→α₂→β→d.