Formation of HCN+ in Heterogeneous Reactions of N2 + and N+ with Surface Hydrocarbons

A significant increase of the ion yield at m/z 27 in collisions of low-energy ions of N2 + and N+ with hydrocarbon-covered room-temperature or heated surfaces of tungsten, carbon-fiber composite, and beryllium, not observed in analogous collisions of Ar+, is ascribed to the formation of HCN+ in heterogeneous reactions between N2 + or N+ and surface hydrocarbons. The formation of HCN+ in the reaction with N+ indicated an exothermic reaction with no activation barrier, likely to occur even at very low collision energies. In the reaction with N2 +, the formation of HCN+ was observed to a different degree on these room-temperature and heated (150 and 300 °C) surfaces at incident energies above about 50 eV. This finding suggested an activation barrier or reaction endothermicity of the heterogeneous reaction of about 3–3.5 eV. The main process in N2 + or N+ interaction with the surfaces is ion neutralization; the probability of forming the reaction product HCN+ was very roughly estimated for both N2 + and N+ ions to about one in 104 collisions with the surfaces.