Heterogeneous reactions between ions NH${}_3$${}^{+}$ and NH${}^{+}$ and hydrocarbons adsorbed on a tungsten surface. Formation of HCN${}^{+}$ in NH${}^{+}$-surface hydrocarbons collisions

Abstract

Interaction of NH${}_3$${}^{+}$ (ND${}_3$${}^{+}$) and NH${}^{+}$ with a hydrocarbon-covered tungsten surface kept at room temperature and heated to 150°C and 300°C showed a series of reactions between the projectile ion and hydrocarbons adsorbed on the tungsten surface. Collisions with NH3+ and particularly with ND3+ showed formation of NH${}_4$${}^{+}$, HCNH${}^{+}$, and CH${}_2$NH${}_2$${}^{+}$ and ND${}_3$H+, HCND${}^{+}$, and CH${}_2$ND${}_2$${}^{+}$, respectively, with NH${}_4$${}^{+}$ (ND${}_3$H${}^{+}$) strongly prevailing at low incident energies of the projectile ion. No formation of HCN${}^{+}$ (DCN${}^{+}$) could be positively identified. In reactions with NH${}^{+}$ formation of HCN${}^{+}$ was clearly observed; the dependence of the HCN${}^{+}$ normalized ion yield on incident energy seems to indicate a threshold at about 40 eV which may be due to an activation energy or an endothermicity of the surface reaction of about 2.4-3.2 eV.

14 pages, 6 figures