Off-normal emission of N₂ produced by desorption mediated reaction of NO on Pd(110) surface

NO molecules adsorbed on a Pd(110) surface undergo desorption with maxima at approximately 495 K at low coverage but two desorption peaks at approximately 370 K and 495 K at high coverage. Desorption of NO at 495 K mediates the emission of N₂ and N₂O. However, desorption of NO at 370 K produces neither N₂ nor N₂O. NO molecules desorbed at 495 K obey cos θ towards the 〈001〉 direction, whereas the N₂ molecules emitted at 495 K have a very sharp spatial distribution 37° off-normal to the surface in the 〈001〉 direction. The emission of N₂ has a full width at half maximum (FWHM) of 19° which can be represented by cos⁴⁶(θ - 37). The spatial distributions of N₂ and NO in the 〈11̄0〉 direction, however, obey cos^4.2θ and cos^1.6θ, respectively.