ON THE RECOMBINATIVE DESORPTION OF N-2 FROM AG(111)

Nitrogen atoms have been adsorbed onto a Ag(lll) surface using a disch arge powered, atomic beam source. At coverages close to saturation a d iffuse (2 x 2) low energy electron diffraction pattern was obtained af ter annealing close to the desorption temperature. Recombinative desor ption occurs with first order thermal desorption peaks near 406 and 44 3 K and an activation energy of 106 and 130 kJ mol(-1), respectively. Angular distributions of recombinatively desorbed N-2 reveal an extrem ely sharp peak along the surface normal, P(theta)=Cos(75)theta, indica ting a large energy release into translation perpendicular to the surf ace. State resolved measurements of the N-2(upsilon, J) distribution u sing resonance enhanced multiphoton ionization were unable to detect d esorption into levels of N-2(upsilon=0, 1, J), indicating that desorpt ion produces a rotationally or vibrationally hot N-2 internal state di stribution. (C) 1997 Elsevier Science B.V.