On the recombinative desorption of N-2 from Ag(111)

Nitrogen atoms have been adsorbed onto a Ag(lll) surface using a discharge powered, atomic beam source. At coverages close to saturation a diffuse (2 x 2) low energy electron diffraction pattern was obtained after annealing close to the desorption temperature. Recombinative desorption occurs with first order thermal desorption peaks near 406 and 443 K and an activation energy of 106 and 130 kJ mol(-1), respectively. Angular distributions of recombinatively desorbed N-2 reveal an extremely sharp peak along the surface normal, P(theta)=Cos(75)theta, indicating a large energy release into translation perpendicular to the surface. State resolved measurements of the N-2(upsilon, J) distribution using resonance enhanced multiphoton ionization were unable to detect desorption into levels of N-2(upsilon=0, 1, J), indicating that desorption produces a rotationally or vibrationally hot N-2 internal state distribution. (C) 1997 Elsevier Science B.V.