Atomic steps and reaction intermediates in chemical reactions

2 Atomic steps and reaction intermediates in chemical reactions 

Early field ion emission studies of gas-surface interactions use field ionization mass spectrometry. Gas molecules are supplied continuously to the tip surface by a polarization force and by the hopping motion of the molecules on the tip surface and along the tip shank. These molecules are subsequently field ionized. The role of the emitter surface in chemical reactions is not transparent and has not been investigated in detail. Only in recent pulsed-laser stimulated field desorption studies with atom-probes are these questions addressed in detail. We now discuss briefly a preliminary study of reaction intermediates in NH3 formation in pulsed-laser stimulated field desorption of co-adsorbed hydrogen and nitrogen, 

In pulsed-laser stimulated field desorption, if the field is high enough, the adsorbed species can be thermally field desorbed, most probably within one to a few atomic vibrations. If the activation barrier of evaporation has been reduced by the applied field to much less than the surface diffusion barrier, then the adsorbed species will be desorbed before they have any chance of interacting with other atoms or molecules on the surface. Thus the desorbed species should represent well the 

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