Abstract
In a recent study of the adsorption of NH3 on Ni(111) at T∠190 K using angle‐resolved UPS, it was concluded that NH3 is molecularly adsorbed, and is bonded to the surface via the N atom with the H atoms oriented away from the surface. To study the bonding configuration using a direct and independent technique, we have examined NH3 on Ni(111) using the electron stimulated desorption ion angular distribution (ESDIAD) method, coupled with temperature programmed desorption (TPD) and low‐energy electron diffraction (LEED). For NH3 coverages achievable at T≳150 K, the ESDIAD patterns are dominated by a ’’halo’’ of ion emission with little ion yield normal to the surface; the halo pattern is consistent with molecular NH3 bonded to Ni via the N atom. Whereas angle‐resolved UPS data indicate a specific azimuthal registry of NH3 with Ni(111), a well‐defined azimuthal orientation is not evident from the ESDIAD results. Possible reasons for the differences between these results are examined, including final state eff...
Published Version
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