HIGH-RESOLUTION ELECTRON-ENERGY-LOSS SPECTROSCOPY STUDY OF CHEMISORBED AND PHYSISORBED N-2 ON RU(1010)

The adsorption of N-2 on Ru(10 (1) over bar 0) has been investigated by means of high-resolution electron energy loss spectroscopy (HREELS) and low-energy electron diffraction (LEED). At 90 K, chemisorbed N-2 is found with an energy of 35 meV for the v(cs)(Ru-N-2) stretching vibration and of 272 meV for the v(cs)(N-N) stretching vibration. A (2 X 3) LEED pattern is observed and a model proposed assuming a N-2 coverage theta(N2) approximate to 0.5. At 20 K, additionally physisorbed N-2 is observed with the v(ps)(N-N) stretching mode at 289 meV. Physisorbed N-2 coexists with the chemisorbed N-2 in the first layer. It is vibrationally excited via negative ion resonance scattering. Surprisingly, both physisorbed and chemisorbed N-2 exhibit the same resonance energy of 1.7 eV.