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Abstract:
The dissociative chemisorption of nitrogen on the Ru(10̅10) surface has been studied using
high-resolution electron energy loss spectroscopy (HREELS), thermal desorption spectroscopy (TDS) and low-energy electron diffraction (LEED). To prepare a surface covered by atomic nitrogen we have used ionization-gauge assisted adsorption. A saturation coverage of θN=0.6 is achieved of which about 30% is in the subsurface region. At saturation coverage a (-1/2 1/1) pattern is observed. Then v ǁ(Ru–N) mode at 41 meV and the v_l_(Ru–N) mode at 60 meV are identified. Upon exposing the nitrogen covered surface to hydrogen at 300 K we have observed the formation of NH3 which is characterized by its symmetric bending mode
δs(NH3) at 149 meV. At 400 K, NH3 could not be detected. The reaction intermediate NH is stable up to 450 K and has been
identified by its vibrational losses ν(Ru–NH) at 86 meV, and ν(N–H) at 408 meV. The TD spectra of mass 14 show three desorption states of nitrogen, Nα at 740 K (from subsurface N), Nβ shifting
from 690 to 640 K with increasing coverage, and Nϒ at 550 K. The activation energy for desorption
via the Nβ state is 120±10 kJ/mol. The TD spectra of mass two showed three desorption states at
450, 550, and 650 K due to the decomposition of NHx.
