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Abstract

Using the chemical shift in the N 1s photoemission peak from the two inequivalent N atoms of N2 adsorbed on Ni(100) we have performed a scanned-energy mode photoelectron diffraction (PhD) structure determination of the Ni(100)c(2x2)–N2 weak chemisorption system. The N2 is found to adsorb atop surface Ni atoms with the N–N axis perpendicular to the surface at a Ni–N nearest-neighbour distance of 1.81 ± 0.02 Å. This is very significantly shorter than the value (2.25 Å) found in an earlier published study. An independent density-functional theory slab calculation yields a value of 1.79 Å, in excellent agreement with the results of the current experiment. Analysis of the PhD modulations of the N 1s photoemission satellite peak show that these are consistent with this comprising separable components localised at the two N atoms as has previously been assumed in an earlier investigation based on (angle-scan) X-ray photoelectron diffraction. Both experiment and theory indicate a small extension of the N–N distance due to the adsorption (0.03 ± 0.03 Å and 0.02 Å respectively).