MOLECULAR AND DISSOCIATIVE CHEMISORPTION OF N2 ON NI(110)

Nitrogen is chemisorbed molecularly by Ni(110) at low temperatures and pressure in two stages. The first stage with a binding energy of ∼35 kJ mol-1 leads to a maximum surface potential of 0.1 V and gives an infrared absorption band initially at 2194 cm-1 and shifting very little with coverage. Further adsorption gives a more weakly bound, ∼27 kJ mol-1, second stage in which the surface potential falls but the infrared band hardly changes. These two stages can be desorbed by warming to 186 K. At higher pressures and temperatures evidence for strongly bound nitrogen is provided by therma1 desorption peaks at 470 and 800 K attributed to dissociatively adsorbed nitrogen. Nitrogen adsorbed at lower temperatures undergoes ordering at 500 K to produce a p(2 × 3) LEED pattern which is tentatively attributed to a surface nitride. © 1979.