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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 θ_N=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
δ_s(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, N_α at 740 K (from subsurface N), N_β shifting
from 690 to 640 K with increasing coverage, and N_ϒ at 550 K. The activation energy for desorption
via the N_β 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 NH_x.