Resonance-like phenomena in activated dissociative adsorption: N+2 on Ni(100) and Ni(111)

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Abstract
Atomic nitrogen adsorption on Ni(100) and Ni(111) surfaces was studied by using very low energy (1–20 eV) N+2 and N+ ion beams. The amount of adsorbed nitrogen was measured by Auger electron spectroscopy as a function of the incident energy of the ions. The adsorption rate for N+ is almost a constant, whereas the dissociative‐adsorption rate for N+2 is strongly energy dependent. In the latter case, there exist two channels; one has a low apparent activation barrier of about 1 eV and the other of about 5 eV. A resonance‐like feature in the low‐activation‐barrier reaction was observed at the incident energy of 2–3 eV on Ni(100) and ∼4 eV on Ni(111). The adsorption rate is independent of the angle of incidence. The resonance‐like feature is explained by a model which assumes that electronically excited molecules produced by resonance neutralization of the incident ions are dissociatively adsorbed over the low activation barrier and the excited molecules are deexcited on the surface at higher incident energies.